Bupropion as a modulator of drug activity

ABSTRACT

Dosage forms, drug delivery systems, and methods related to sustained release of dextromethorphan or improved therapeutic effects are disclosed. Typically, bupropion or a related compound is orally administered to a human being to be treated with, or being treated with, dextromethorphan.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/950,838, filed Nov. 17, 2020, which is acontinuation-in-part of U.S. patent application Ser. No. 16/821,462,filed Mar. 17, 2020, now U.S. Pat. No. 10,874,663; which is acontinuation-in-part of U.S. patent application Ser. No. 16/359,958,filed Mar. 20, 2019, now U.S. Pat. No. 10,881,657; which is acontinuation-in-part of U.S. patent application Ser. No. 15/821,563,filed Nov. 22, 2017, now U.S. Pat. No. 10,512,643; which is acontinuation-in-part of U.S. patent application Ser. No. 15/645,939,filed Jul. 10, 2017, now U.S. Pat. No. 9,867,819; which is acontinuation-in-part of U.S. patent application Ser. No. 15/263,138,filed on Sep. 12, 2016, now U.S. Pat. No. 9,700,553; which is acontinuation of U.S. patent application Ser. No. 15/164,746, filed onMay 25, 2016, now U.S. Pat. No. 9,457,023; which is acontinuation-in-part of U.S. patent application Ser. No. 14/879,002,filed Oct. 8, 2015, now U.S. Pat. No. 9,375,429; which is a continuationof U.S. patent application Ser. No. 14/554,988, filed Nov. 26, 2014, nowU.S. Pat. No. 9,205,083; which is a continuation of U.S. patentapplication Ser. No. 14/550,618, filed Nov. 21, 2014, now U.S. Pat. No.9,198,905; which is a continuation-in-part of International Pat. App.No. PCT/US2014/064184, filed Nov. 5, 2014; which claims the benefit ofU.S. Prov. Pat. App. No. 61/900,354, filed Nov. 5, 2013; U.S. patentapplication Ser. No. 15/821,563 also claims the benefit of U.S. Prov.Pat. App. No. 62/576,538, filed Oct. 24, 2017; U.S. patent applicationSer. No. 16/950,838 is also a continuation-in-part of U.S. patentapplication Ser. No. 16/894,713, filed Jun. 5, 2020, now U.S. Pat. No.10,898,453; which is a continuation-in-part of U.S. patent applicationSer. No. 16/838,829, filed on Apr. 2, 2020, now U.S. Pat. No.10,772,850; which is a continuation-in-part of U.S. patent applicationSer. No. 16/359,996, filed Mar. 20, 2019, now U.S. Pat. No. 10,688,066;which claims the benefit of U.S. Prov. Pat. App. No. 62/645,751, filedMar. 20, 2018; U.S. patent application Ser. No. 16/838,829 is also acontinuation-in-part of U.S. patent application Ser. No. 16/107,472,filed Aug. 21, 2018, now U.S. Pat. No. 10,806,710; which is acontinuation of U.S. patent application Ser. No. 15/688,660, filed Aug.28, 2017, now U.S. Pat. No. 10,058,518; which is a continuation of U.S.patent application Ser. No. 15/213,283, filed on Jul. 18, 2016, nowabandoned; which is a continuation-in-part of U.S. patent applicationSer. No. 15/057,983, filed Mar. 1, 2016, now U.S. Pat. No. 9,408,815;which is a continuation-in-part of U.S. patent application Ser. No.14/863,284, filed Sep. 23, 2015, now U.S. Pat. No. 9,278,095; which is acontinuation of U.S. patent application Ser. No. 14/604,397, filed Jan.23, 2015, now U.S. Pat. No. 9,168,234; which is a continuation of U.S.patent application Ser. No. 14/602,177, filed Jan. 21, 2015, now U.S.Pat. No. 9,402,843; which is a continuation-in-part of U.S. patentapplication Ser. No. 14/550,618, filed Nov. 21, 2014, now U.S. Pat. No.9,198,905; which is a continuation-in-part of International Pat. App.No. PCT/US2014/064184, filed Nov. 5, 2014; which claims the benefit ofU.S. Prov. Pat. App. No. 61/900,354, filed Nov. 5, 2013; U.S. patentapplication Ser. No. 15/213,283 also claims the benefit of U.S. Prov.Pat. App. Nos. 62/323,438, filed Apr. 15, 2016; 62/313,620, filed Mar.25, 2016; and 62/313,067, filed Mar. 24, 2016; all of the aboveapplications, U.S. patents issued from, or U.S. publications of any ofthe above applications are incorporated by reference in their entirety.

SUMMARY

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being, comprising co-administering bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds with dextromethorphan.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being, comprising co-administeringerythrohydroxybupropion or a prodrug thereof, with dextromethorphan tothe human being, wherein the erythrohydroxybupropion or a prodrugthereof is administered in an amount that results in an AUC₀₋₁₂ ofdextromethorphan that is at least about 40 ng·hr/mL.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being, comprising co-administeringerythrohydroxybupropion or a prodrug thereof, with dextromethorphan tothe human being, wherein the erythrohydroxybupropion or a prodrugthereof is administered in an amount that results in a C_(max) ofdextromethorphan that is at least about 6 ng/mL.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being, comprising co-administeringerythrohydroxybupropion or a prodrug thereof, with dextromethorphan tothe human being, wherein the erythrohydroxybupropion or a prodrugthereof is administered in an amount that results in a C_(avg) ofdextromethorphan, over the period between two separate and consecutiveadministrations of dextromethorphan, that is at least about 5 ng/mL.

Some embodiments include a method of increasing the metabolic lifetimeof dextromethorphan, comprising administering threohydroxybupropion, ora prodrug thereof, to a human being in need of treatment withdextromethorphan, wherein the human being is an extensive metabolizer ofdextromethorphan, and wherein dextromethorphan is present in the body ofthe human being at the same time as threohydroxybupropion.

Some embodiments include a method of reducing an adverse eventassociated with treatment by dextromethorphan, comprisingco-administering threohydroxybupropion, or a prodrug thereof, anddextromethorphan to a human patient in need of dextromethorphantreatment, wherein the human patient is at risk of experiencing theadverse event as a result of being treated with dextromethorphan.

Some embodiments include an oral sustained release delivery system fordextromethorphan, comprising bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a prodrug of any ofthese compounds, dextromethorphan, and a water soluble vehicle.

Some embodiments include a method of decreasing the number of doses ofdextromethorphan that can be administered without loss of efficacy,comprising orally administering an effective amount of bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or aprodrug of any of these compounds, to a human being in need of treatmentwith dextromethorphan.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need of treatment withdextromethorphan, wherein the threohydroxybupropion, or a prodrugthereof, is administered on the first day of at least two days oftreatment with dextromethorphan, wherein a decrease in the dextrorphanplasma level occurs on the first day that threohydroxybupropion, or aprodrug thereof, and dextromethorphan are co-administered, as comparedto the same amount of dextromethorphan administered withoutthreohydroxybupropion or a prodrug thereof.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need of treatment withdextromethorphan, wherein the hydroxybupropion, or a prodrug thereof, isadministered on the first day of at least two days of treatment withdextromethorphan, wherein a decrease in the dextrorphan plasma leveloccurs on the first day that hydroxybupropion, or a prodrug thereof, anddextromethorphan are co-administered, as compared to the same amount ofdextromethorphan administered without hydroxybupropion or a prodrugthereof.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering bupropion and dextromethorphan to ahuman being in need of treatment with dextromethorphan, wherein thebupropion is administered on the first day of at least two days oftreatment with dextromethorphan, wherein a decrease in the dextrorphanplasma level occurs on the first day that bupropion and dextromethorphanare co-administered, as compared to the same amount of dextromethorphanadministered without bupropion.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need of treatment withdextromethorphan, wherein the erythrohydroxybupropion, or a prodrugthereof, is administered on the first day of at least two days oftreatment with dextromethorphan, wherein a decrease in the dextrorphanplasma level occurs on the first day that erythrohydroxybupropion, or aprodrug thereof, and dextromethorphan are co-administered, as comparedto the same amount of dextromethorphan administered withouterythrohydroxybupropion or a prodrug thereof.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least eight consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the eighth day, the dextrorphanplasma level is lower than the dextrorphan plasma level that would havebeen achieved by administering the same amount of dextromethorphanadministered without bupropion for eight consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least eight consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theeighth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without hydroxybupropion, or aprodrug thereof, for eight consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least eight consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theeighth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without erythrohydroxybupropion,or a prodrug thereof, for eight consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least eight consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theeighth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without threohydroxybupropion,or a prodrug thereof, for eight consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least nine consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the ninth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without hydroxybupropion, or aprodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without erythrohydroxybupropion,or a prodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without threohydroxybupropion,or a prodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least nine consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the ninth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without hydroxybupropion, or aprodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without erythrohydroxybupropion,or a prodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without threohydroxybupropion,or a prodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least nine consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the ninth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without hydroxybupropion, or aprodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without erythrohydroxybupropion,or a prodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least nine consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on theninth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without threohydroxybupropion,or a prodrug thereof, for nine consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least ten consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the tenth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion for ten consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least ten consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thetenth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without hydroxybupropion, or aprodrug thereof, for ten consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least ten consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thetenth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without erythrohydroxybupropion,or a prodrug thereof, for ten consecutive days.

Some embodiments include a method of decreasing dextrorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least ten consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thetenth day, the dextrorphan plasma level is lower than the dextrorphanplasma level that would have been achieved by administering the sameamount of dextromethorphan administered without threohydroxybupropion,or a prodrug thereof, for ten consecutive days.

Antidepressant compounds, such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, can be used to improve thetherapeutic properties, such as in the treatment of neurologicaldisorders, of dextromethorphan. Bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, regardless of stereochemistry, can beeffective in inhibiting or reducing the metabolism of dextromethorphanin some human beings. This may be accomplished by co-administeringbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan.

Some embodiments include a method of treating a neurological disordercomprising administering: 1) dextromethorphan, or 2) a combination of anantidepressant compound and dextromethorphan to a human being in needthereof, wherein the human being is an extensive metabolizer ofdextromethorphan.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being in need of treatment with dextromethorphan,wherein the human being is an extensive metabolizer of dextromethorphan,comprising co-administering bupropion with dextromethorphan to the humanbeing.

Some embodiments include a method of inhibiting the metabolism ofdextromethorphan, comprising administering bupropion to a human being,wherein the human being is an extensive metabolizer of dextromethorphan,and wherein dextromethorphan is present in the body of the human beingat the same time as bupropion.

Some embodiments include a method of increasing the metabolic lifetimeof dextromethorphan, comprising administering bupropion to a human beingin need of treatment with dextromethorphan, wherein the human being isan extensive metabolizer of dextromethorphan, and whereindextromethorphan is present in the body of the human being at the sametime as bupropion.

Some embodiments include a method of correcting extensive metabolism ofdextromethorphan, comprising administering bupropion to a human being inneed thereof.

Some embodiments include a method of improving the antitussiveproperties of dextromethorphan comprising administering bupropion inconjunction with administration of dextromethorphan to a human being inneed of treatment for cough.

Some embodiments include a method of treating cough comprisingadministering a combination of bupropion or another active compound anddextromethorphan to a human being in need thereof.

Some embodiments include a method of treating a neurological disordercomprising administering 1) dextromethorphan, or 2) bupropion anddextromethorphan to a human being in need thereof, wherein the 1)dextromethorphan, or 2) bupropion and dextromethorphan are administeredat least once a day for at least 8 days, at least 9 days, or at least 10days.

Some embodiments include a method of treating a neurological disordercomprising administering about 150 mg/day to about 300 mg/day ofbupropion and about 15 mg/day to about 60 mg/day of dextromethorphan toa human being in need thereof.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being in need of treatment with dextromethorphan,wherein the human being is an extensive metabolizer of dextromethorphan,comprising co-administering hydroxybupropion, or a prodrug thereof, withdextromethorphan to the human being.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being in need of treatment with dextromethorphan,wherein the human being is an extensive metabolizer of dextromethorphan,comprising co-administering erythrohydroxybupropion, or a prodrugthereof, with dextromethorphan to the human being.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being in need of treatment with dextromethorphan,wherein the human being is an extensive metabolizer of dextromethorphan,comprising co-administering threohydroxybupropion, or a prodrug thereof,with dextromethorphan to the human being.

Some embodiments include a method of inhibiting metabolism ofdextromethorphan, comprising administering bupropion to a human being,wherein the human being is an extensive metabolizer of dextromethorphan,and wherein dextromethorphan is present in the body of the human beingat the same time as bupropion.

Some embodiments include a method of inhibiting metabolism ofdextromethorphan, comprising administering hydroxybupropion, or aprodrug thereof, to a human being, wherein the human being is anextensive metabolizer of dextromethorphan, and wherein dextromethorphanis present in the body of the human being at the same time ashydroxybupropion.

Some embodiments include a method of inhibiting metabolism ofdextromethorphan, comprising administering erythrohydroxybupropion, or aprodrug thereof, to a human being, wherein the human being is anextensive metabolizer of dextromethorphan, and wherein dextromethorphanis present in the body of the human being at the same time aserythrohydroxybupropion.

Some embodiments include a method of inhibiting metabolism ofdextromethorphan, comprising administering threohydroxybupropion, or aprodrug thereof, to a human being, wherein the human being is anextensive metabolizer of dextromethorphan, and wherein dextromethorphanis present in the body of the human being at the same time asthreohydroxybupropion.

Some embodiments include a method of increasing the metabolic lifetimeof dextromethorphan, comprising administering hydroxybupropion, or aprodrug thereof, to a human being in need of treatment withdextromethorphan, wherein the human being is an extensive metabolizer ofdextromethorphan, and wherein dextromethorphan is present in the body ofthe human being at the same time as hydroxybupropion.

Some embodiments include a method of increasing the metabolic lifetimeof dextromethorphan, comprising administering erythrohydroxybupropion,or a prodrug thereof, to a human being in need of treatment withdextromethorphan, wherein the human being is an extensive metabolizer ofdextromethorphan, and wherein dextromethorphan is present in the body ofthe human being at the same time as erythrohydroxybupropion.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering bupropion and dextromethorphan to ahuman being in need of treatment with dextromethorphan, wherein thebupropion is administered on the first day of at least two days ofco-administration of bupropion with dextromethorphan, wherein anincrease in the dextromethorphan plasma level occurs on the first daythat bupropion and dextromethorphan are co-administered, as compared tothe same amount of dextromethorphan administered without bupropion.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need of treatment withdextromethorphan, wherein the hydroxybupropion, or a prodrug thereof, isadministered on the first day of at least two days of co-administrationof hydroxybupropion, or a prodrug thereof, with dextromethorphan,wherein an increase in the dextromethorphan plasma level occurs on thefirst day that hydroxybupropion, or a prodrug thereof, anddextromethorphan are co-administered, as compared to the same amount ofdextromethorphan administered without hydroxybupropion or a prodrugthereof.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need of treatment withdextromethorphan, wherein the erythrohydroxybupropion, or a prodrugthereof, is administered on the first day of at least two days ofco-administration of erythrohydroxybupropion, or a prodrug thereof, withdextromethorphan, wherein an increase in the dextromethorphan plasmalevel occurs on the first day that erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan are co-administered, as compared to thesame amount of dextromethorphan administered withouterythrohydroxybupropion or a prodrug thereof.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need of treatment withdextromethorphan, wherein the threohydroxybupropion, or a prodrugthereof, is administered on the first day of at least two days ofco-administration of threohydroxybupropion, or a prodrug thereof, withdextromethorphan, wherein an increase in the dextromethorphan plasmalevel occurs on the first day that threohydroxybupropion, or a prodrugthereof, and dextromethorphan are co-administered, as compared to thesame amount of dextromethorphan administered withoutthreohydroxybupropion or a prodrug thereof.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least five consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the fifth day, the dextromethorphanplasma level is higher than the dextromethorphan plasma level that wouldhave been achieved by administering the same amount of dextromethorphanadministered without bupropion for five consecutive days.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least five consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thefifth day, the dextromethorphan plasma level is higher than thedextromethorphan plasma level that would have been achieved byadministering the same amount of dextromethorphan administered withouthydroxybupropion, or a prodrug thereof, for five consecutive days.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least five consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thefifth day, the dextromethorphan plasma level is higher than thedextromethorphan plasma level that would have been achieved byadministering the same amount of dextromethorphan administered withouterythrohydroxybupropion, or a prodrug thereof, for five consecutivedays.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least five consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thefifth day, the dextromethorphan plasma level is higher than thedextromethorphan plasma level that would have been achieved byadministering the same amount of dextromethorphan administered withoutthreohydroxybupropion, or a prodrug thereof, for five consecutive days.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering bupropion and dextromethorphan, forat least six consecutive days, to a human being in need of treatmentwith dextromethorphan, wherein, on the sixth day, the dextromethorphanplasma level is higher than the dextromethorphan plasma level that wouldhave been achieved by administering the same amount of dextromethorphanadministered without bupropion for six consecutive days.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering hydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least six consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thesixth day, the dextromethorphan plasma level is higher than thedextromethorphan plasma level that would have been achieved byadministering the same amount of dextromethorphan administered withouthydroxybupropion, or a prodrug thereof, for six consecutive days.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least six consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thesixth day, the dextromethorphan plasma level is higher than thedextromethorphan plasma level that would have been achieved byadministering the same amount of dextromethorphan administered withouterythrohydroxybupropion, or a prodrug thereof, for six consecutive days.

Some embodiments include a method of increasing dextromethorphan plasmalevels comprising co-administering threohydroxybupropion, or a prodrugthereof, and dextromethorphan, for at least six consecutive days, to ahuman being in need of treatment with dextromethorphan, wherein, on thesixth day, the dextromethorphan plasma level is higher than thedextromethorphan plasma level that would have been achieved byadministering the same amount of dextromethorphan administered withoutthreohydroxybupropion, or a prodrug thereof, for six consecutive days.

Some embodiments include a method of reducing a trough effect ofdextromethorphan comprising, co-administering bupropion withdextromethorphan to a human patient in need of treatment withdextromethorphan, wherein dextromethorphan has a plasma level 12 hoursafter co-administering bupropion with dextromethorphan that is at leasttwice the plasma level that would be achieved by administering the sameamount of dextromethorphan without bupropion.

Some embodiments include a method of reducing a trough effect ofdextromethorphan comprising, co-administering hydroxybupropion, or aprodrug thereof, with dextromethorphan to a human patient in need oftreatment with dextromethorphan, wherein dextromethorphan has a plasmalevel 12 hours after co-administering hydroxybupropion, or a prodrugthereof, with dextromethorphan that is at least twice the plasma levelthat would be achieved by administering the same amount ofdextromethorphan without hydroxybupropion or a prodrug thereof.

Some embodiments include a method of reducing a trough effect ofdextromethorphan comprising, co-administering erythrohydroxybupropion,or a prodrug thereof, with dextromethorphan to a human patient in needof treatment with dextromethorphan, wherein dextromethorphan has aplasma level 12 hours after co-administering erythrohydroxybupropion, ora prodrug thereof, with dextromethorphan that is at least twice theplasma level that would be achieved by administering the same amount ofdextromethorphan without erythrohydroxybupropion or a prodrug thereof.

Some embodiments include a method of reducing a trough effect ofdextromethorphan comprising, co-administering threohydroxybupropion, ora prodrug thereof, with dextromethorphan to a human patient in need oftreatment with dextromethorphan, wherein dextromethorphan has a plasmalevel 12 hours after co-administering threohydroxybupropion, or aprodrug thereof, with dextromethorphan that is at least twice the plasmalevel that would be achieved by administering the same amount ofdextromethorphan without threohydroxybupropion or a prodrug thereof.

Some embodiments include a method of reducing an adverse eventassociated with treatment by dextromethorphan, comprisingco-administering bupropion and dextromethorphan to a human patient inneed of dextromethorphan treatment, wherein the human patient is at riskof experiencing the adverse event as a result of being treated withdextromethorphan.

Some embodiments include a method of reducing an adverse eventassociated with treatment by dextromethorphan, comprisingco-administering hydroxybupropion, or a prodrug thereof, anddextromethorphan to a human patient in need of dextromethorphantreatment, wherein the human patient is at risk of experiencing theadverse event as a result of being treated with dextromethorphan.

Some embodiments include a method of reducing an adverse eventassociated with treatment by dextromethorphan, comprisingco-administering erythrohydroxybupropion, or a prodrug thereof, anddextromethorphan to a human patient in need of dextromethorphantreatment, wherein the human patient is at risk of experiencing theadverse event as a result of being treated with dextromethorphan.

Some embodiments include a method of reducing an adverse eventassociated with treatment by bupropion, comprising co-administeringdextromethorphan and bupropion to a human patient in need of bupropiontreatment, wherein the human patient is at risk of experiencing theadverse event as a result of being treated with bupropion.

Some embodiments include a method of correcting extensive metabolism ofdextromethorphan, comprising administering hydroxybupropion, or aprodrug thereof, to a human being in need thereof.

Some embodiments include a method of correcting extensive metabolism ofdextromethorphan, comprising administering erythrohydroxybupropion, or aprodrug thereof, to a human being in need thereof.

Some embodiments include a method of correcting extensive metabolism ofdextromethorphan, comprising administering threohydroxybupropion, or aprodrug thereof, to a human being in need thereof.

Some embodiments include a method of improving antitussive properties ofdextromethorphan comprising administering bupropion in conjunction withadministration of dextromethorphan to a human being in need of treatmentfor cough.

Some embodiments include a method of improving antitussive properties ofdextromethorphan comprising administering hydroxybupropion, or a prodrugthereof, in conjunction with administration of dextromethorphan to ahuman being in need of treatment for cough.

Some embodiments include a method of improving antitussive properties ofdextromethorphan comprising administering erythrohydroxybupropion, or aprodrug thereof, in conjunction with administration of dextromethorphanto a human being in need of treatment for cough.

Some embodiments include a method of improving antitussive properties ofdextromethorphan comprising administering threohydroxybupropion, or aprodrug thereof, in conjunction with administration of dextromethorphanto a human being in need of treatment for cough.

Some embodiments include a method of treating cough comprisingadministering a combination of hydroxybupropion, or a prodrug thereof,and dextromethorphan to a human being in need thereof.

Some embodiments include a method of treating cough comprisingadministering a combination of erythrohydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need thereof.

Some embodiments include a method of treating cough comprisingadministering a combination of threohydroxybupropion, or a prodrugthereof, and dextromethorphan to a human being in need thereof.

Some embodiments include a method of treating a neurological disordercomprising administering bupropion and dextromethorphan to a human beingin need thereof, wherein the bupropion and dextromethorphan areadministered at least once a day for at least 8 days, at least 9 days,or at least 10 days.

Some embodiments include a method of treating a neurological disordercomprising administering hydroxybupropion, or a prodrug thereof, anddextromethorphan to a human being in need thereof, wherein the bupropionand dextromethorphan are administered at least once a day for at least 8days, at least 9 days, or at least 10 days.

Some embodiments include a method of treating a neurological disordercomprising administering erythrohydroxybupropion, or a prodrug thereof,and dextromethorphan to a human being in need thereof, wherein theerythrohydroxybupropion and dextromethorphan are administered at leastonce a day for at least 8 days, at least 9 days, or at least 10 days.

Some embodiments include a method of treating a neurological disordercomprising administering threohydroxybupropion, or a prodrug thereof,and dextromethorphan to a human being in need thereof, wherein thethreohydroxybupropion and dextromethorphan are administered at leastonce a day for at least 8 days, at least 9 days, or at least 10 days.

Some embodiments include a pharmaceutical composition, dosage form, ormedicament comprising a therapeutically effective amount ofdextromethorphan, a therapeutically effective amount of anantidepressant, such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, and a pharmaceutically acceptableexcipient.

Some embodiments include a method of reducing a risk of seizureassociated with use of bupropion to treat depression, comprising orallyadministering a dextromethorphan-bupropion combination twice a day,wherein the method is: 1) at least as effective in treating depression,and 2) reduces the risk of seizure to the human being, as compared toorally administering 150 mg of the bupropion alone twice a day to thehuman being for the same number of days.

Some embodiments include a method of improving the therapeutic effect ofbupropion in treating depression, comprising orally co-administering adextromethorphan with a bupropion, twice a day, to a human beingsuffering from depression, wherein the method is more effective thantreating the depression of that human being by orally administering 150mg of the bupropion alone twice a day to the human being for five weeks.

In some embodiments, the combination of the dextromethorphan and thebupropion is more effective than independently orally administering thesame amount of the dextromethorphan or the bupropion alone.

Some embodiments include a method of improving the efficacy of bupropionin treating depression, comprising orally administering about 90 mg toabout 125 mg of a bupropion in combination with about 0.3 mg/kg to about1 mg/kg of a dextromethorphan, once or twice a day for at least 23 days,to a human being suffering from depression, wherein orally administeringthe bupropion in combination with the dextromethorphan is more effectivein treating depression than orally administering the same dosage regimenof bupropion without dextromethorphan.

Some embodiments include a method of treating treatment-resistantdepression comprising: selecting a human being suffering from depressionwho has previously been unsuccessfully treated with at least oneantidepressant; and orally administering a dextromethorphan-bupropioncombination treatment once or twice a day to the human being for atleast about five weeks; wherein the dextromethorphan-bupropioncombination treatment comprises about 40 mg to about 70 mg of adextromethorphan and about 100 mg to about 140 mg of a bupropion.

Some embodiments include a method of rapidly relieving the symptoms ofdepression, comprising administering a combination of bupropion anddextromethorphan once daily or twice daily to a human being in needthereof, wherein the human being experiences a therapeutic effect within2 weeks of the first day that the combination of bupropion anddextromethorphan is administered.

Some embodiments include a method of treating depression, comprisingadministering a combination of bupropion and dextromethorphan once dailyor twice daily to a human being in need thereof, wherein the human beingis of Asian descent.

Some embodiments include a method of treating nicotine addictionassociated with smoking tobacco comprising administering a combinationof a bupropion and a dextromethorphan daily for at least 21 consecutivedays to a person suffering from nicotine addiction, wherein the personis an ad-lib tobacco smoker, wherein a total amount of 200 mg to 250 mgof bupropion and 80 mg to 140 mg of dextromethorphan are administered tothe person daily, and wherein the method is more effective thanadministering the same amount of bupropion alone.

In some embodiments involving treating nicotine addiction,administration of the combination of the bupropion and thedextromethorphan results in at least 20% greater reduction in anintensity of the nicotine self-administration as compared to bupropionalone as measured by the reduction in the average number of cigarettessmoked per day.

In some embodiments involving treating nicotine addiction,administration of the combination of the bupropion and thedextromethorphan results in at least 10% greater reduction in expiredcarbon monoxide levels as compared to bupropion alone.

In some embodiments involving treating nicotine addiction, administeringthe combination of the bupropion and the dextromethorphan twice a day in2 equal divided doses results in a greater reduction in intensity ofnicotine self-administration at a particular timepoint, such as 1 week,2 weeks, 3 weeks, 4 weeks, or another timepoint recited herein, thanwould have resulted from administering one of the 2 divided doses forthe same amount of time, or than would have resulted from notadministering the combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of the mean plasma concentrations of dextromethorphanover time after dosing on Day 8 for subjects administereddextromethorphan alone or dextromethorphan and bupropion.

FIG. 2 depicts mean AUC₀₋₁₂ of dextromethorphan on Day 8 for subjectsadministered dextromethorphan alone or dextromethorphan and bupropion.

FIG. 3 depicts mean AUC₀₋₂₄ of dextromethorphan on Day 8 for subjectsadministered dextromethorphan alone or dextromethorphan and bupropion.

FIG. 4 depicts mean AUC_(0-inf) of dextromethorphan on Day 8 forsubjects administered dextromethorphan alone or dextromethorphan andbupropion.

FIG. 5 depicts the fold changes in AUCs of dextromethorphan on Day 8 forsubjects administered dextromethorphan alone as compared todextromethorphan and bupropion.

FIG. 6 depicts mean AUC₀₋₁₂ of dextromethorphan on Day 1 and Day 8 forsubjects administered dextromethorphan alone or dextromethorphan andbupropion.

FIG. 7 depicts mean dextromethorphan trough plasma concentrations forsubjects administered dextromethorphan alone or dextromethorphan andbupropion.

FIG. 8 depicts mean dextromethorphan maximum plasma concentrations onDay 1 and Day 8 for subjects administered dextromethorphan alone ordextromethorphan and bupropion.

FIG. 9 is a plot of the mean plasma concentrations of dextrorphan overtime after dosing on Day 8 for subjects administered dextromethorphanalone or dextromethorphan and bupropion.

FIG. 10 depicts mean dextrorphan maximum plasma concentrations on Day 1and Day 8 for subjects administered dextromethorphan alone ordextromethorphan and bupropion.

FIG. 11 depicts mean AUC₀₋₁₂ of dextrorphan on Day 1 and Day 8 forsubjects administered dextromethorphan alone or dextromethorphan andbupropion.

FIG. 12 depicts the potency of various antidepressant compounds forinhibition of the metabolism of dextromethorphan in human livermicrosomes.

FIG. 13 is a plot of the average MADRS total score change from baselineover time during the 6-week dosing period for subjects administeredbupropion alone or the combination of dextromethorphan and bupropion.

FIG. 14 depicts the percent of subjects achieving remission (MADRS≤10)over time during the 6-week dosing period for subjects administeredbupropion alone or the combination of dextromethorphan and bupropion.

FIG. 15 is a plot of the reduction in MADRS total score over time forthe subjects described in Example 6.

FIG. 16 is a plot of the percentage of responders over time for thesubjects described in Example 6.

FIG. 17 is a plot of the percentage of subjects in remission over timefor the subjects described in Example 6.

FIG. 18 is a plot of the MADRS total score change from baseline overtime for the subjects described in Example 7.

FIG. 19 is a plot of the QIDS-SR-16 total score change from baselineover time for the subjects described in Example 7.

FIG. 20 is a plot of the percentage of subjects in remission (QIDS-SR-16Score≤5) over time for the subjects described in Example 7.

FIG. 21 is a plot of the Cognitive Items of MGH-CPFQ change frombaseline over time for the subjects described in Example 7.

FIG. 22 is a plot of the CMAI total score change from baseline over timefor the subjects described in Example 8.

FIG. 23 is a plot of the percent CMAI reduction from baseline over timefor the subjects described in Example 8.

FIG. 24 is a plot of is a plot of the percentage of responders with CMAIreduction ≥30% from baseline over time for the subjects described inExample 8.

FIG. 25 depicts the reduction in MADRS Score from baseline from theclinical trial of DM/BU in Example 10 as compared to the combination ofdextromethorphan and quinidine (DM/Q) as reported in Murrough (Journalof Affective Disorders 218 (2017) 277-283, FIG. 3A).

DETAILED DESCRIPTION

Some embodiments include a method of treating neurological disorderscomprising administering a therapeutically effective amount ofdextromethorphan and a therapeutically effective amount of anantidepressant, such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, to a person in need thereof.

Some embodiments include a method of enhancing the therapeuticproperties of dextromethorphan in treating neurological disorders,comprising co-administering dextromethorphan and an antidepressant, suchas bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds.

Some embodiments include a method of increasing dextromethorphan plasmalevels in a human being that is an extensive metabolizer ofdextromethorphan, comprising co-administering an antidepressantcompound, such as bupropion, and dextromethorphan to the human being.

Some embodiments include a method of inhibiting the metabolism ofdextromethorphan, comprising administering an antidepressant compound,such as bupropion, to a human being, wherein the human being is anextensive metabolizer of dextromethorphan, and wherein dextromethorphanis present in the body of the human being at the same time as theantidepressant.

Some embodiments include a method of increasing the metabolic lifetimeof dextromethorphan, including increasing the elimination half-life(T_(1/2)) of dextromethorphan. These embodiments may compriseadministering an antidepressant compound, such as bupropion, to a humanbeing, wherein the human being is an extensive metabolizer ofdextromethorphan, and wherein dextromethorphan is present in the body ofthe human being at the same time as the antidepressant compound.

Some embodiments include a method of correcting extensive metabolism ofdextromethorphan, comprising administering an antidepressant compound,such as bupropion, to a human being in need thereof, such as a humanbeing in need of treatment for pain.

Some embodiments include a method of improving the therapeuticproperties of dextromethorphan in treating neurological disorderscomprising administering an antidepressant compound, such as bupropion,in conjunction with administration of dextromethorphan to a human beingin need of treatment for a neurological disorder.

Some embodiments include a method of treating neurological disorderscomprising administering a combination of an antidepressant compound,such as bupropion, and dextromethorphan to a human being in needthereof.

Co-administration of an antidepressant compound, such as bupropion,hydroxybupropion, threohydroxybupropion, erythrohydroxybupropion, or aprodrug of the antidepressant compound, with dextromethorphan may occurone or more times for a single day, or for 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100, or more consecutive days.In some embodiments, co-administration is at least daily for at leasttwo consecutive days.

In some embodiments, co-administration of an antidepressant compound,such as bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a prodrug of the antidepressant compound,with dextromethorphan may occur once a day for 1, 2, 3, 4, 5, 6, or 7days, prior to co-administration twice a day.

Dextromethorphan has the structure shown below.

Dextromethorphan is used as a cough suppressant. According to the FDA'sdextromethorphan product labeling requirement under the OTC Monograph[21CFR341.74], dextromethorphan should be dosed 6 times a day (every 4hours), 4 times a day (every 6 hours), or 3 times a day (every 8 hours).The OTC Monograph [21CFR341.74] also states that “the dosage isequivalent to dextromethorphan hydrobromide . . . [o]ral dosage is 10 to20 milligrams every 4 hours or 30 milligrams every 6 to 8 hours, not toexceed 120 milligrams in 24 hours, or as directed by a doctor.”

Dextromethorphan is rapidly metabolized in the human liver. This rapidhepatic metabolism may limit systemic drug exposure in individuals whoare extensive metabolizers. Human beings can be: 1) extensivemetabolizers of dextromethorphan—those who rapidly metabolizedextromethorphan; 2) poor metabolizers of dextromethorphan—those whoonly poorly metabolize dextromethorphan; or 3) intermediate metabolizersof dextromethorphan—those whose metabolism of dextromethorphan issomewhere between that of an extensive metabolizer and a poormetabolizer. Extensive metabolizers can also be ultra-rapidmetabolizers. Extensive metabolizers of dextromethorphan are asignificant portion of the human population. Dextromethorphan can, forexample, be metabolized to dextrorphan.

When given the same oral dose of dextromethorphan, plasma levels ofdextromethorphan are significantly higher in poor metabolizers orintermediate metabolizers as compared to extensive metabolizers ofdextromethorphan. The low plasma concentrations of dextromethorphan canlimit its clinical utility as a single agent for extensive metabolizers,and possibly intermediate metabolizers, of dextromethorphan. Sometherapeutically active compounds, including antidepressants such asbupropion, inhibit the metabolism of dextromethorphan, and raise theplasma concentration of dextromethorphan, and can thus improve itstherapeutic efficacy. Similarly, antidepressants may allowdextromethorphan to be given less often, such as once a day instead oftwice a day, once a day instead of three times a day, once a day insteadof four times a day, twice a day instead of three times a day, or twicea day instead of four times a day, without loss of therapeutic efficacy.

Co-administration of an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, with dextromethorphanor dextrorphan may enhance the mechanisms of action, or pharmacologicalproperties of dextromethorphan and dextrorphan. Mechanisms of action ofdextromethorphan and dextrorphan can include sigma-1 agonist and NMDAantagonist properties, calcium channel blockade, muscarinic binding,serotonin transporter (5HTT) inhibition, and mu receptor potentiation.

Some embodiments include co-administration of an antidepressant such asbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, with dextromethorphan or dextrorphan to agonize, antagonize,or modulate a sigma-1 receptor, or an NMDA receptor; to block a calciumchannel; to bind to a muscarinic receptor; to inhibit a serotonintransporter (5HTT); or to potentiate a mu receptor.

Pharmacological properties of dextromethorphan and dextrorphan caninclude NMDA high-affinity site, NMDR-2A, and functional NMDR-2Breceptor antagonism, sigma-1 stimulation, putative mTOR activation (bysigma-1 stimulation, mu potentiation, beta adrenoreceptor stimulation,and 5HTT inhibition), putative AMPA receptor trafficking (by mTORactivation, PCP antagonism, sigma-1 stimulation, beta stimulation, mupotentiation, and 5HTT inhibition), and dendritogenesis, spinogenesis,synaptogenesis, and neuronal survival by NMDA antagonism and sigma-1 andmTOR signaling. Some embodiments include co-administration of anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, with dextromethorphan or dextrorphanto bind to, agonize, antagonize, stimulate, activate, inhibit, influencethe trafficking of, or modulate an NMDA high-affinity site, NMDR-2A, afunctional NMDR-2B receptor, sigma-1 receptor, a putative mTOR receptor(such as by stimulating sigma-1, potentiating a mu receptor, stimulatinga beta adrenoreceptor, or inhibiting a 5HTT), or a putative AMPAreceptor (such as by activating mTOR, antagonizing PCP activity,stimulating a sigma-1 receptor, stimulating a beta adrenergic receptor,potentiating a mu receptor, or inhibiting 5HTT). Some embodimentsinclude co-administration of an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, with dextromethorphanor dextrorphan to cause, increase, decrease, or otherwise modulatedendritogenesis, spinogenesis, or synaptogenesis. Some embodimentsinclude co-administration of an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, with dextromethorphanor dextrorphan to cause, increase, decrease, or otherwise modulateneuronal survival by NMDA antagonism and/or sigma-1 and/or mTORsignaling.

Pharmacological properties of dextromethorphan and dextrorphan caninclude 5HTT and norepinephrine transporter inhibition, sigma-1stimulation, NMDA and PCP antagonism, and possible serotonin 5HT1b/dreceptor stimulation. Some embodiments include co-administration of anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, with dextromethorphan or dextrorphanto bind to, agonize, antagonize, stimulate, activate, inhibit, influencethe trafficking of, or modulate the 5HTT and/or norepinephrinetransporter, the sigma-1 receptor, NMDA and/or PCP receptor, and/or tostimulate the serotonin 5HT1b/d receptor.

Additional properties for dextromethorphan and dextrorphan can includepossible presynaptic alpha-2 adrenoreceptor antagonism or postsynapticalpha-2 stimulation, beta stimulation and possible muscarinic and muantagonism. Some embodiments include co-administration of anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, with dextromethorphan or dextrorphanto bind to, agonize, antagonize, stimulate, activate, inhibit, influencethe trafficking of, or modulate a presynaptic alpha-2 adrenoreceptor,postsynaptic alpha-2 receptor, beta adrenoreceptor, muscarinic receptor,or mu receptor. Dextromethorphan and dextrorphan may be glial cellmodulators. Some embodiments include co-administration of anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, with dextromethorphan or dextrorphanto modulate glial cells.

Pain or other neurological disorders may be treated by enhancingdextromethorphan plasma levels or increasing dextromethorphanbioavailability, for example by a method comprising administering atherapeutically effective amount of dextromethorphan and atherapeutically effective amount of an antidepressant compound, such asbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, to a person in need thereof.

Examples of neurological disorders that may be treated, or that may betreated with increased efficacy, by enhanced dextromethorphan levels,such as those achievable by a combination of dextromethorphan and anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, include, but are not limited to:affective disorders, psychiatric disorders, cerebral function disorders,movement disorders, dementias, motor neuron diseases, neurodegenerativediseases, seizure disorders, and headaches.

Affective disorders that may be treated by enhanced dextromethorphanlevels or by a combination of dextromethorphan and an antidepressantsuch as bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, include, but are not limited to, depression, majordepression, treatment resistant depression and treatment resistantbipolar depression, bipolar disorders including cyclothymia, seasonalaffective disorder, mood disorders, chronic depression (dysthymia),psychotic depression, postpartum depression, premenstrual dysphoricdisorder (PMDD), situational depression, atypical depression, mania,anxiety disorders, attention deficit disorder (ADD), attention deficitdisorder with hyperactivity (ADDH), and attention deficit/hyperactivitydisorder (AD/HD), bipolar and manic conditions, obsessive-compulsivedisorder, bulimia, obesity or weight-gain, narcolepsy, chronic fatiguesyndrome, premenstrual syndrome, substance addiction or abuse, nicotineaddiction, psycho-sexual dysfunction, pseudobulbar affect, and emotionallability.

Depression may be manifested by depressive symptoms. These symptoms mayinclude psychological changes such as changes in mood, feelings ofintense sadness, despair, mental slowing, loss of concentration,pessimistic worry, agitation, anxiety, irritability, guilt, anger,feelings of worthlessness, reckless behavior, suicidal thoughts orattempts, and/or self-deprecation. Physical symptoms of depression mayinclude insomnia, anorexia, appetite loss, weight loss, weight gain,decreased energy and libido, fatigue, restlessness, aches, pains,headaches, cramps, digestive issues, and/or abnormal hormonal circadianrhythms.

Some patients, even after treatment with medications such asantidepressants, may have an inadequate or no response to the treatment.Treatment resistant depression (TRD), or treatment-refractorydepression, is a condition generally associated with patients who havefailed treatment with at least two antidepressants. Part of thediagnosis for TRD is for the patient to have had an inadequate responseto treatment with the antidepressants after an adequate dose andadequate course, e.g. in the current depressive episode. TRD may be moredifficult to treat due to the comorbidity of other medical orpsychological illnesses, such as drug/alcohol abuse or eating disorders,or TRD being misdiagnosed. Some TRD patients have had an inadequateresponse to 1, 2, 3, or more adequate antidepressant treatment trials orhave failed or had an inadequate response to 1, 2, 3, or more priorantidepressant treatments. In some embodiments, a patient being treatedfor treatment resistant depression has failed treatment with at least 1,2, 3, 4, 5, 6, 7, 8, 9, 10, or more antidepressant therapies.

Measures of treatment effect that may be improved by treatment withenhanced bioavailability or plasma levels of dextromethorphan, or by acombination of dextromethorphan and an antidepressant, such asbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, include, but are not limited to: Montgomery-Asberg DepressionRating Scale (MADRS), Quality of Life Enjoyment and SatisfactionQuestionnaire Short Form, Range of Impaired Functioning Tool, SheehanDisability Scale, Patient Rated Inventory of Side Effects (PRISE),Columbia-Suicide Severity Rating Scale (C-SSRS), Quick Inventory ofDepressive Symptomatology, Self-Report (QIDS-SR), Clinical GlobalImpression (CGI) scale, Massachusetts General Hospital Cognitive andPhysical Functioning Questionnaire (CPFQ), 17-item Hamilton Rating Scalefor Depression (HAM-D17), Massachusetts General Hospital AntidepressantTreatment Response Questionnaire (MGH ATRQ), 16-item Quick Inventory ofDepressive Symptomatology—Self Report (QIDS-SR16), Sheehan DisabilityScale (SDS), Clinical Global Impression of Severity of Illness (CGI-S),Clinical Global Impression of Change (CGI-C), EuroQOL 5 Dimension 5Level (EQ-5D-5L), Patient Global Impression of Change (PGIC), 7-itemGeneralized Anxiety Disorder (GAD-7), Clinical GlobalImpressions-Improvement (CGI-I). Sheehan Disability Scale (SDS). 16-itemQuick Inventory of Depressive Symptomatology—Self Report (QIDS-SR16),Hamilton Anxiety Scale (HAM-A), Massachusetts General Hospital Cognitiveand Physical Functioning Questionnaire (CPFQ), CPFQ-Cognitive subscales(Items 4 to 7), Brief Psychiatric Rating Scale (BPRS), etc.; DigitSymbol Substitution Test (DSST), Rey Auditory Verbal Learning Task(RAVLT), Trail Making Test (TMT), Stroop Colour Naming Test (STROOP),Simple Reaction Time (SRT), Choice Reaction Time (CRT). etc. In someembodiments, treating a person with a combination of dextromethorphanand bupropion may improve (e.g. reduce) the person's score in one of theabove assessments by at least about 10%, at least about 20%, at leastabout 30%, at least about 40%, at least about 50%, about 10-20%, about20-30%, about 30-40%, about 40-50%, about 5-15%, about 15-25%, about25-35%, about 35-45%, about 45-55%, about 50-60%, about 60-70%, about70-80%, about 80-90%, about 90-100% as compared to baseline or placebo.In some embodiments, the improvement is compared to baseline. In someembodiments, the improvement is compared to placebo.

Administering a combination of bupropion and dextromethorphan may resultin a rapid treatment effect, e.g. within about 1 week, within about 2weeks, within about 3 weeks, or within about 4 weeks of beginning thetreatment. For example, an improvement in any of the assessmentsdescribed herein, including, but not limited to MADRS, Quality of LifeEnjoyment and Satisfaction Questionnaire Short Form, Range of ImpairedFunctioning Tool, PRISE, C-SSRS, QIDS-SR), CGI, CPFQ, HAM-D17, MGH ATRQ,CGI-S, CGI-C, EQ-5D-5L, PGIC, GAD-7, CGI-I, SDS, QIDS-SR16, HAM-A, CPFQ,CPFQ-Cognitive subscales (Items 4 to 7), BPRS, DSST, RAVLT, TMT, STROOP,SRT, CRT, etc., may be observed within those time periods.

In some embodiments, an enhanced bioavailability of dextromethorphan, ora combination of dextromethorphan and an antidepressant such asbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, may have an onset of action within 30 minutes, 1 hour, 2hours, 3 hours, 4 hours, 5 hours, 6 hours, 6-8 hours, 8-12 hours, 12hours, a day, 1-7 days, 1 week, two weeks, three weeks, four weeks, sixweeks, or eight weeks.

Patients who may benefit from the treatments described herein includepediatric patients, such as patients under about 18 years of age, about0-5 years of age, about 5-10 years of age, about 10-12 years of age, orabout 12-18 years of age; adult patients, such as patients having an ageof about 18-70 years, about 18-65 years, about 18-30 years, about 10-20years, about 20-30 years, about 30-40 years, about 40-50 years, about50-60 years, about 60-70 years, about 70-80 years, about 80-90 years,about 30-50 years, about 50-65 years; elderly patients, such as patientsover 65 years of age, about 65-75 years of age, about 75-90 years ofage, or over 90 years of age; and about 41 years of age or older.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, is, oris selected for being, of Asian descent. In some embodiments, the humanbeing that is treated with a combination of dextromethorphan andbupropion, e.g. for a type of depression, is, or is selected for being,of Japanese descent. In some embodiments, the human being that istreated with a combination of dextromethorphan and bupropion, e.g. for atype of depression, is, or is selected for being, of Korean descent. Insome embodiments, the human being that is treated with a combination ofdextromethorphan and bupropion, e.g. for a type of depression, is, or isselected for being, of Chinese descent. The assignment of an individualas having Asian, Chinese, Japanese, or Korean descent may be based uponself-reporting by the individual. In these Asian individuals, thecombination of dextromethorphan and bupropion may be effective fortreating depression where bupropion alone is not. This may be ofparticular importance because patients of Asian descent may suffer frommore severe depression than those of other ethnic or cultural groups.

In some embodiments, the human being does not have, or is selected fornot having, a depressive episode with psychotic or catatonic features.

In some embodiments, the human being does not have, or is selected fornot having, a manic, hypomanic or mixed episode, including bipolardisorder (Type 1 or Type 2) and substance-induced (e.g.antidepressant-induced) manic, or a hypomanic/mixed episode.

In some embodiments, the human being does not have, or is selected fornot having schizophrenia, schizoaffective, or another psychoticdisorder.

In some embodiments, the human being does not have, or is selected fornot having, a panic disorder, with or without agoraphobia.

In some embodiments, the human being does not have, or is selected fornot having obsessive-compulsive disorder.

In some embodiments, the human being does not have, or is selected fornot having bulimia or anorexia nervosa.

In some embodiments, the human being does not have, or is selected fornot having, a persistent neurocognitive disorder.

In some embodiments, the human being does not have, or is selected fornot having, any anxiety disorder for the six months prior to treatment.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a diagnosis with major depressive disorderaccording to the Diagnostic and Statistical Manual of Mental Disorders,Fourth Edition, Text Revision (DSM-IV-TR), the Structured ClinicalInterview for Diagnostic and Statistical Manual of Mental Disorders,Fifth Edition, Clinical Trials Version SCID-5-CT. In some embodiments,the human being currently meets the DSM-5 criteria for MDD withoutpsychotic features, based on the SCID-5-CT

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, issuffering from, or is selected for suffering from, a major depressiveepisode that has lasted between about 8 weeks and about 24 months, about1-6 months, about 6-12 months, about 1-2 years, at least about 1 week,at least about 2 weeks, at least about 3 weeks, at least about 4 weeks,at least about 6 weeks, at least about 2 months, at least about 3months, at least about 4 months, at least about 6 months, at least about9 months, at least about 1 year, at least about 18 months, at leastabout 2 years, about 1-12 weeks, about 3-6 months, about 6-9 months,about 9-12 months, about 12-18 months, about 18-24 months, about 2-4years, about 4-6 years, about 6-10 years, about 10-20 years or longer.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected having, about 1-100, or more, lifetime depressiveepisodes, such as a major depressive episodes, including at least 1, atleast about 2, at least about 3, at least about 4, at least about 5, atleast about 10, at least about 15, at least about 20, at least about 30,at least about 40, at least about 50, at least about 60, at least about70, at least about 80, at least about 90, at least about 100, about 1-5,about 5-10, about 10-20, about 20-30, about 30-40, about 40-50, about50-60, about 60-70, about 70-80, about 80-90, about 90-100, or about 4-7lifetime depressive episodes.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, an inadequate response to one or more priorantidepressant therapies, e.g. 1, 2, 3, 4, 5 or more priorantidepressant therapies, including prior antidepressant therapies inthe current depressive episode (e.g. the current major depressiveepisode).

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, hashad, or is selected for having had a background antidepressant therapywith, such as a selective serotonin reuptake inhibitor (SSRI), aserotonin norepinephrine reuptake inhibitor (SNRI), or bupropion, takenat an adequate dose for at least 8 weeks, and at a stable dose for atleast 4 weeks prior to entering the double-blind treatment period. Insome embodiments, the antidepressant therapy is continued in conjunctionwith treatment with the combination of bupropion and dextromethorphan.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, is, oris selected for being male. In some embodiments, the human being that istreated with a combination of dextromethorphan and bupropion, e.g. for atype of depression, is, or is selected for being female.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a body mass index of about 18-40 kg/m², about18.5 kg/m², less than 18.5 kg/m², about 19 kg/m², about 19-24.9 kg/m²,about 25 kg/m², about 25-29 kg/m², about 29 kg/m², more than 29 kg/m²,about 18-22 kg/m², about 22-24 kg/m², about 24-26 kg/m², about 26-28kg/m², about 28-30 kg/m², about 30-32 kg/m², about 32-34 kg/m², about34-36 kg/m², about 36-38 kg/m², about 38-40 kg/m², about 18-26 kg/m²,about 26-34 kg/m², or about 34-40 kg/m².

The MADRS is a clinician-rated scale. The MADRS is used to assessdepressive symptomatology during the previous week. Subjects are ratedon 10 items to assess feelings of guilt, sadness, lassitude, pessimism,inner tension, suicidality, reduced sleep or appetite, agitation,anxiety, weight loss, somatic symptoms, difficulty concentrating andlack of interest. Each item is scored on a 7-point scale. A score of 0indicates the absence of symptoms, and a score of 6 indicates symptomsof maximum severity.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a MADRS score that is at least about 25, atleast about 30, at least about 35, at least about 40, at least about 45,at least about 50, at least about 55, about 20-25, about 25-30, about30-35, about 35-40, about 40-45, about 45-50, about 50-55, about 55-60,about 25-35, about 35-45, about 45-60, about 25-40, or about 40-60.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a MADRS score that isreduced by at least about 10%, at least about 20%, at least about 30%,at least about 40%, at least about 50%, about 10-20%, about 20-30%,about 30-40%, about 40-50%, about 50-60%, about 60-80%, about 80-90%, orabout 90-100% as compared to baseline or placebo. In some embodiments,the reduction is compared to baseline. In some embodiments, thereduction is compared to placebo.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a MADRS score that isless than 34, about 20-34, about 7-19, about 0-6, about 30 or less,about 26 or less, about 25 or less, about 20 or less, about 17 or less,about 14 or less, about 12 or less, about 10 or less, about 8 or less,about 6 or less, about 5 or less, about 4 or less, about 3 or less,about 2 or less, about 1 or less, about 0, about 0.1-6, about 0.1-1,about 1-2, about 2-3, about 3-4, about 4-5, about 5-6, about 6-7, about7-8, about 8-9, about 9-10, about 10-11, about 11-12, about 12-13, about13-14, about 14-15, about 15-16, about 16-17, about 17-18, about 18-19,about 19-20, about 18-20, about 0.1-3, about 3-6, about 6-9, about 9-12,about 12-14, about 12-15, or about 15-20.

The subscale MADRS-6 is the sum of responses to six of the 10 MADRSitems that are thought to represent the core symptoms of depression:reported sadness, apparent sadness, inner tension, lassitude, inabilityto feel, and pessimistic thoughts. MADRS items not included in theMADRS-6 score are reduced sleep, reduced appetite, concentrationdifficulties, and suicidal thoughts. Higher MADRS score indicates moresevere depression, and each item yields a score of 0 to 6. The overallscore ranges from 0 to 60. The questionnaire includes questions on thefollowing symptoms 1. Apparent sadness 2. Reported sadness 3. Innertension 4. Reduced sleep 5. Reduced appetite 6. Concentrationdifficulties 7. Lassitude 8. Inability to feel 9. Pessimistic thoughts10. Suicidal thoughts. Usual cutoff points are: a) 0 to 6—normal/symptomabsent; b) 7 to 19—mild depression; c) 20 to 34—moderate depression; andd) >34—severe depression.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a MADRS-6 score that is at least about 15, atleast about 18, at least about 20, at least about 21, at least about 24,at least about 27, at least about 30, at least about 33, about 15-18,about 18-21, about 21-24, about 24-27, about 27-30, about 30-33, about30-34, about 33-36, at least about 34, about 7-19, about 15-19, about15-24, about 24-30, about 20-34, or about 30-36, prior to starting thetreatment.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a MADRS-6 score reducedby at least about 10%, at least about 20%, at least about 30%, at leastabout 40%, or at least about 50%, about 10-20%, about 20-30%, about30-40%, about 40-50%, about 50-60%, about 60-80%, about 80-90%, or about90-100% as compared to baseline or placebo. In some embodiments, thereduction is compared to baseline. In some embodiments, the reduction iscompared to placebo.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a MADRS-6 score that isabout 17 or less, about 15 or less, about 10 or less, about 8 or less,about 6 or less, about 5 or less, about 4 or less, about 3 or less,about 2 or less, about 1 or less, about 0.1-6, about 0.1-1, about 1-2,about 2-3, about 3-4, about 4-5, about 5-6, about 6-7, about 7-8, about8-9, about 9-12, about 12-15, about 0.1-3, about 3-6, about 6-8, about6-9, or about 9-15.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a score for item 1 (Apparent sadness) on theMADRS that is 2, 4, or 6, prior to starting the treatment.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a reduction of the scorefor item 1 on the MADRS that is at least about 10%, at least about 20%,at least about 30%, at least about 40%, or at least about 50% ascompared to baseline or placebo. In some embodiments, the reduction iscompared to baseline. In some embodiments, the reduction is compared toplacebo.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a score on item 1 of theMADRS that is about 2 or less.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-6, weeks 4-6, weeks 6-8, weeks8-12, weeks 12-16, at the end of week 1, at the beginning or at the endof week 2, at the beginning or at the end of week 3, at the beginning orat the end of week 4, at the beginning or at the end of week 5, at thebeginning or at the end of week 6, at the beginning or at the end ofweek 7, at the beginning or at the end of week 8, at the beginning or atthe end of week 9, at the beginning or at the end of week 10, at thebeginning or at the end of week 11, at the beginning or at the end ofweek 12, at the beginning or at the end of week 13, at the beginning orat the end of week 14, at the beginning or at the end of week 15, at thebeginning or at the end of week 16, or at any other time. In someembodiments, the treatment effect is assessed weekly using the MADRS.

The CGI-S scale is a clinician-rated scale used to rate the severity ofthe subject's current state of mental illness compared with a subjectpopulation with MDD. The subject is rated on a scale from 1 to 7, with 1indicating a “normal state” and 7 indicating “among the most extremelyill subjects.” The CGI-S may be administered by a person with extensiveprofessional training and experience in assessing mental illness.Possible ratings are: 1) Normal, not at all ill; 2) Borderline mentallyill; 3) Mildly ill; 4) Moderately ill; 5) Markedly ill; 6) Severely ill;and 7) Among the most extremely ill patients.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a Clinical Global Impression-Severity (CGI-S)score that is at least about 3, at least about 4, at least about 5, atleast about 6, about 7, about 3-7, about 4-7, about 3-4, about 4-5,about 5-6, or about 6-7.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the CGI-Sscore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the CGI-Sscore that is at least about 1, at least about 2, at least about 3, atleast about 4, at least about 5, about 0.1-6, about 0.1-1, about 1-2,about 2-3, about 3-4, about 4-5, about 5-6, about 0.1-3, or about 3-6.In some embodiments, the reduction is compared to baseline. In someembodiments, the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-6, weeks 2-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The 16-item QIDS-SR-16, a patient-rated scale, is an abbreviated versionof the 30-item Inventory of Depressive Symptomatology (IDS) and isdesigned to assess the severity of depressive symptoms. The QIDS-SR-16assesses criterion symptom domains to diagnose a major depressiveepisode.

The QIDS-SR may be used to assess the subject's depressivesymptomatology over the prior 7 days. Subjects report severity ofsymptoms on 10 items: sleep, feelings of sadness, appetite, weightchange, concentration, self-regard, suicidality, general interest level,energy level, psychomotor retardation, and restlessness. Each item maybe scored on a 4-point scale with a score of 0 reflecting no symptomsand a score of 3 reflecting symptoms of maximum severity.

Total QIDS scores range from 0 to 27, with scores of 5 or lowerindicative of no depression, scores from 6 to 10 indicating milddepression, 11 to 15 indicating moderate depression, 16 to 20 reflectingsevere depression, and total scores greater than 21 indicating verysevere depression.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a QIDS-SR-16 score that is at least about 16,at least about 18, at least about 21, at least about 24, at least about27, at least about 30, at least about 33, about 16-18, about 16-19,about 16-20, about 18-21, about 21-24, about 24-27, about 15-21, orabout 21-27, prior to starting the treatment.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in theQIDS-SR-16 score that is at least about 10%, at least about 20%, atleast about 30%, at least about 40%, or at least about 50% as comparedto baseline or placebo. In some embodiments, the reduction is comparedto baseline. In some embodiments, the reduction is compared to placebo.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a QIDS-SR-16 score thatis about 6 or less, about 5 or less, about 4 or less, about 3 or less,about 2 or less, about 1 or less, about 0.1-6, about 0.1-5, about 0.1-1,about 1-2, about 2-3, about 3-4, about 4-5, about 5-6, about 0.1-3, orabout 3-6. Treatment effect may be assessed at any appropriate time,such as during weeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6,weeks 4-6, weeks 6-8, weeks 8-12, weeks 12-16, at the beginning or atthe end of week 1, at the beginning or at the end of week 2, at thebeginning or at the end of week 3, at the beginning or at the end ofweek 4, at the beginning or at the end of week 5, at the beginning or atthe end of week 6, at the beginning or at the end of week 7, at thebeginning or at the end of week 8, at the beginning or at the end ofweek 9, at the beginning or at the end of week 10, at the beginning orat the end of week 11, at the beginning or at the end of week 12, at thebeginning or at the end of week 13, at the beginning or at the end ofweek 14, at the beginning or at the end of week 15, at the beginning orat the end of week 16, or at any other time.

The CGI-I scale is a clinician-rated scale that is used to rate totalimprovement or worsening of mental illness regardless of whether theInvestigator considers it to be a result of drug treatment or not. Thesubject is rated on a scale from 1 to 7, with 1 indicating that thesubject is very much improved and 7 indicating that the subject is verymuch worse. The CGI-I may be administered by a person with extensiveprofessional training and experience in assessing mental illness.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a CGI-I score that isabout 3 or less, about 2 or less, about 1, about 1-2, or about 2-3.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The VAMS is a patient-rated mood scale consisting of a 100-mm line withgraphical, schematic, or pictorial representations of extremes of mood,e.g. happiness and sadness, at the two ends of the line, such as a sadface at one end and a happy face at the other end. Each end of the linemay be further anchored by a word statement which describe the extremesof mood. Subjects are asked to rate their mood as a mark on the line.The distance on the line is measured and calculated as a numerical scorefrom 0 to 100. Subjects may be asked to complete the VAMS daily.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a VAMS score that is at least about 40 mm, atleast about 50 mm, at least about 60 mm, at least about 70 mm, at leastabout 80 mm, at least about 90 mm, about 40-50 mm, about 50-60 mm, about60-70 mm, about 70-80 mm, about 80-90 mm, about 90-100 mm, about 40-60mm, about 60-80 mm, or about 80-100 mm.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the VAMSscore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

In some embodiments, treatment with the combination of dextromethorphanand bupropion results in the human being having a VAMS score that isless than about 50 mm, less than about 40 mm, less than about 30 mm,less than about 20 mm, less than about 10 mm, about 0-10 mm, about 10-20mm, about 20-30 mm, about 30-40 mm, about 40-50 mm, about 0-25 mm, orabout 25-50 mm.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The Columbia Suicide Severity Rating Scale (C-SSRS) is a clinician-ratedinstrument that reports the severity of both suicidal ideation andbehavior. Suicidal ideation is classified on a 5-item scale: 1 (wish tobe dead), 2 (nonspecific active suicidal thoughts), 3 (active suicidalideation with any methods [not plan] without intent to act), 4 (activesuicidal ideation with some intent to act, without specific plan), and 5(active suicidal ideation with specific plan and intent). The C-SSRSalso captures information about the intensity of ideation, specificallythe frequency, duration, controllability, deterrents, and reasons forthe most severe types of ideation. Suicidal behavior is classified on a5-item scale: 0 (no suicidal behavior), 1 (preparatory acts orbehavior), 2 (aborted attempt), 3 (interrupted attempt), and 4 (actualattempt). More than 1 classification can be selected provided theyrepresent separate episodes. For actual attempts only, the actual orpotential lethality is classified for the initial, most lethal, and mostrecent attempts.

The C-SSRS may be administered each time a person being treated sees ahealth professional. The C-SSRS may be completed for the subject'slifetime history of suicidal ideation and behavior, along with a recentrecall period.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in theColumbia-Suicide Severity Rating Scale (C-SSRS) score that is at leastabout 10%, at least about 20%, at least about 30%, at least about 40%,or at least about 50% as compared to baseline or placebo. In someembodiments, the reduction is compared to baseline. In some embodiments,the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The Sheehan Disability Scale (SDS) is a self-rated instrument used tomeasure the effect of the patient's symptoms on the following threeitems: work/school, social life, and family/home responsibilities. Foreach of the three items, scores range from 0 through 10. The number mostrepresentative of how much each area was disrupted by symptoms is markedalong the line from 0 (not at all) to 10 (extremely). The three items ordomains can be summarized to evaluate global functional impairment byadding the scores of each of the three items or domains, resulting inglobal SDS score ranges from 0 (unimpaired) to 30 (highly impaired).

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a Sheehan Disability Scale (SDS) score thatis: for each item SDS (0-10 scale) at least about 4, at least about 5,at least about 6, at least about 7, at least about 8, at least about 9;and for SDS total score at least about 5, at least 10, at least about20, about 10-15, about 15-20, about 20-25, or about 25-30.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the SDSscore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The Hamilton Rating Scale for Depression (HAM-D, HRSD, HDRS, or HAMD-17)is a clinician-rated, 17-item scale used to rate the subject'sdepressive state based on feelings of depression, guilt, suicidality,anxiety, agitation, level of insight, patterns of insomnia, loss ofinterest in work and other activities, weight loss, hypochondriasis, anddegree of psychomotor retardation. It also can be used to identifygenital, and somatic symptoms. Items are rated either on 0-2 scale or on0-4 scale. A higher score is indicative of more severity. For example,HAM-D score level of depression of 10-13 is considered mild; 14-17 isconsidered mild to moderate; and >17 is considered moderate to severe.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a HAM-D score that is at least about 16, atleast about 19, at least about 21, at least about 24, at least about 27,at least about 30, at least about 33, at least about 36, about 16-19,about 18-21, about 21-24, about 24-27, about 27-30, about 30-33, about33-36, about 36-40, about 15-24, about 24-33, or about 33-40, or morethan 40 prior to starting the treatment.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the HAM-Dscore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time. In some embodiments, the treatment effect is assessedweekly using the HAM-D.

Conversion from MADRS scores to HAM-D scores and vice versa may beaccomplished using the table below.

Total scores Change scores Percentage change scores MADRS HAMD MADRSHAMD MADRS HAMD −100 −98 −98 −94 −96 −92 3 3 −37 −27 −94 −90 4 4 −36 −26−92 −88 5 4 −35 −25 −90 −86 6 5 −34 −25 −88 −84 7 6 −33 −24 −86 −83 8 7−32 −23 −84 −81 9 7 −31 −23 −82 −80 10 8 −30 −22 −80 −79 11 9 −29 −22−78 −77 12 9 −28 −21 −76 −75 13 10 −27 −20 −74 −74 14 11 −26 −20 −72 −7315 12 −25 −19 −70 −72 16 12 −24 −18 −68 −70 17 13 −23 −18 −66 −67 18 14−22 −17 −64 −65 19 15 −21 −16 −62 −62 20 16 −20 −16 −60 −61 21 16 −19−15 −58 −59 22 17 −18 −14 −56 −57 23 18 −17 −14 −54 −56 24 19 −16 −13−52 −54 25 19 −15 −12 −50 −52 26 20 −14 −12 −48 −50 27 21 −13 −11 −46−48 28 22 −12 −10 −44 −47 29 23 −11 −9 −42 −45 30 23 −10 −9 −40 −43 3124 −9 −8 −38 −41 32 25 −8 −7 −36 −39 33 25 −7 −6 −34 −37 34 26 −6 −6 −32−35 35 27 −5 −5 −30 −33 36 28 −4 −4 −28 −31 37 29 −3 −3 −26 −29 38 29 −2−2 −24 −27 39 30 −1 −1 −22 −25 40 31 0 −1 −20 −23 41 32 1 0 −18 −21 4233 2 1 −16 −19 43 34 3 2 −14 −17 44 35 4 2 −12 −15 45 35 5 3 −10 −13 4636 6 4 −8 −11 47 37 7 4 −6 −9 48 37 8 5 −4 −7 49 38 −2 −5 50 38 0 −3 5139 2 0 52 40 4 1 53 40 6 2 8 4 10 5 12 7 14 9 16 10 18 11 20 13 22 15 2417 26 18 28 19 30 20 32 21 34 22 36 24 38 26 40 28 Negative values meanimprovement.

The Hamilton Anxiety Scale (HAM-A) is a clinician-administered scalewhich consists of 14 items, each rated on a five point scale rangingfrom 0 (not present) to 4 (very severe). The highest possible totalscore is 56, which represents the most severe form of anxiety; thelowest possible score is 0, which represents an absence of anxiety.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a Hamilton Anxiety Scale (HAM-A) score thatis at least about 20, at least about 25, at least about 30, at leastabout 35, at least about 40, at least about 45, at least about 50, atleast about 55, about 20-25, about 25-30, about 30-35, about 35-40,about 40-45, about 45-50, about 50-56, about 25-35, about 35-45, about45-56, about 25-40, or about 40-56.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the HAM-Ascore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The Massachusetts General Hospital Cognitive and Physical FunctioningQuestionnaire (CPFQ) is a 7-item patient-rated scale used to measurecognitive and executive dysfunction in mood and anxiety disorders andwas developed to assess clinically relevant cognitive and physicalsymptoms that could emerge or persist during long-term treatment fordepression. Subjects grade the perceived quality of their physical andcognitive functioning. It is scored from 1-6 with increasing severitythat individually evaluates 7 distinct items: motivation/enthusiasm,wakefulness/alertness, energy, focus/attention, recall, ability to findwords, and sharpness/mental acuity. The physical dimension of the CPFQassesses sleepiness and fatigue, and the cognitive dimension assessesapathy, inattention, forgetfulness, word-finding difficulties, andmental slowness. A higher score is indicative of more impairment.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the CPFQscore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in theCPFQ-Cognitive subscales (items 4-7) score that is at least about 10%,at least about 20%, at least about 30%, at least about 40%, or at leastabout 50% as compared to baseline or placebo. In some embodiments, thereduction is compared to baseline. In some embodiments, the reduction iscompared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

The Brief Psychiatric Rating Scale (BPRS) is a clinician-administeredscale developed to measure psychiatric symptoms such as depression,anxiety, hallucinations and unusual behavior. Each symptom is rated from1 (not present) to 7 (extremely severe). Zero is entered if the item isnot assessed and will be excluded from the analysis. The scale should beadministered by a clinician who is knowledgeable concerning psychoticdisorders and able to interpret the constructs used in the assessment.Factor 1 (Reality Distortion) items are Suspiciousness, HallucinatoryBehavior and Unusual Thought Content.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a Brief Psychiatric Rating Scale(BPRS)-Factor 1 score that is starting score: at least about 3, at leastabout 4, at least about 5, at least about 6, about 7, about 3-7, about4-7, about 4-5, about 5-6, or about 6-7.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in theBPRS-Factor 1 score that is at least about 1, at least about 2, at leastabout 3, at least about 4, at least about 5, about 0.1-6, about 0.1-1,about 1-2, about 2-3, about 3-4, about 4-5, about 5-6, about 0.1-3, orabout 3-6 as compared to baseline or placebo. In some embodiments, thereduction is compared to baseline. In some embodiments, the reduction iscompared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, a Beck Depression Inventory (BDI) score thatis at least about 20, at least about 25, at least about 30, at leastabout 35, at least about 40, at least about 45, at least about 50, atleast about 55, at least about 60, about 20-25, about 25-30, about30-35, about 35-40, about 40-45, about 45-50, about 50-55, about 55-60,about 60-63, about 25-35, about 35-45, about 45-55, about 55-63, about25-40, or about 40-63.

The Beck Depression Inventory (BDI, BDI-1A, BDI-II) is a 21-questionmultiple-choice self-report inventory about how the subject has beenfeeling in the last week. Each question had a set of four possibleresponses, ranging in intensity. When the test is scored, a value of 0to 3 is assigned for each answer and then the total score is compared toa key to determine the depression's severity. Higher total scoresindicate more severe depressive symptoms. The standard cut-off scoreswere as follows: 0-9: indicates minimal depression; 10-18: indicatesmild depression; 19-29: indicates moderate depression; and 30-63:indicates severe depression.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having a reduction in the BDIscore that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

In some embodiments, the human being that is treated with a combinationof dextromethorphan and bupropion, e.g. for a type of depression, has,or is selected for having, C Reactive Protein (CRP) levels that are atleast 0.5 mg/L, at least 1 mg/L, at least 2 mg/L, or higher.

In some embodiments, administering the combination of dextromethorphanand bupropion results in the human being having an improvement in CRPlevel that is at least about 10%, at least about 20%, at least about30%, at least about 40%, or at least about 50% as compared to baselineor placebo. In some embodiments, the reduction is compared to baseline.In some embodiments, the reduction is compared to placebo.

Treatment effect may be assessed at any appropriate time, such as duringweeks 1-2, weeks 1-3, weeks 1-4, weeks 1-5, weeks 1-6, weeks 4-6, weeks6-8, weeks 8-12, weeks 12-16, at the beginning or at the end of week 1,at the beginning or at the end of week 2, at the beginning or at the endof week 3, at the beginning or at the end of week 4, at the beginning orat the end of week 5, at the beginning or at the end of week 6, at thebeginning or at the end of week 7, at the beginning or at the end ofweek 8, at the beginning or at the end of week 9, at the beginning or atthe end of week 10, at the beginning or at the end of week 11, at thebeginning or at the end of week 12, at the beginning or at the end ofweek 13, at the beginning or at the end of week 14, at the beginning orat the end of week 15, at the beginning or at the end of week 16, or atany other time.

Conversion between some of the scores in some of the assessments abovemay be done according to the tables below.

Severity IDS-C IDS-SR QIDS-C QIDS-SR HRSD 17 HRSD21 HRSD24 MADRS BDI 00-3 0-3 0 0  0 0-1 0-1 0 0 0 4-5 4-5 1 1 1-2  2  2 0  6  6 2 2  3  3 3-40 7-8 7-8 3 3  4  4  5 0  9-10  9-11 4 4 5-6 5-6 6-7 0 11 12-13 5 5  77-8 8-9 6 9 1 12-15 14-16 6 6  8  9 10-11 7 10 1 16-17 17-18 7 7  9-1010 12 1 18-20 19-21 8 8 11 11-12 13-14 1 21-22 22-23 9 9 12 13 15-16 123 24-25 10 10 13 14-15 17-18 19 18 2 24-27 26-28 11 11 14-15 16 19 2019 2 28-29 29-30 12 12 16 17 20-21 2 30-32 31-33 13 13 17 18-19 22-23 233-35 34-36 14 14 18-19 20-21 24-25 2 36 37-38 15 15 18-19 22 26 34 29 337-39 39-40 16 16 20 23 27-28 35 30 3 40-41 41-43 17 17 21-22 24-2529-30 3 42-43 44-45 18 18 23 26 31-32 3 44-45 46-47 19 19 24 27 33 3 4648 20 20 25 28 34 4 47-51 49-53 21 21 26-27 29-31 35-38 4 52-53 54-55 2222 28 32 39 4 54-56 56-58 23 23 29 33-34 40-41 4 57-59 59-61 24 24 30-3135-36 42-44 4 60-62 62-24 25 25 32 37-38 45-46 4 63-65 65-67 26 26 33-3539-41 47-49 4 66-84 68-84 27 27 36-52 42-64 50-75 60 63 ¹Severity ofDepression. 0 = None, 1 = Mild, 2 = Moderate, 3 = Severe, 4 = VerySevere.

Severity IDS-SR QIDS-SR HRSD 17 HRSD21 HRSD24 0 0-3 0  0 0-1 0-1 0 4-5 11-2  2  2 0  6 2  3  3 3-4 0 7-8 3  4  4  5 0  9-11 4 5-6 5-6 6-7 012-13 5  7 7-8 8-9 1 14-16 6  8  9 10-11 1 17-18 7  9-10 10 12 1 19-21 811 11-12 13-14 1 22-23 9 12 13 15-16 1 24-25 10 13 14-15 17-18 2 26-2811 14-15 16 19 2 29-30 12 16 17 20-21 2 31-33 13 17 18-19 22-23 2 34-3614 18-19 20-21 24-25 2 37-38 15 18-19 22 26 3 39-40 16 20 23 27-28 341-43 17 21-22 24-25 29-30 3 44-45 18 23 26 31-32 3 46-47 19 24 27 33 348 20 25 28 34 4 49-53 21 26-27 29-31 35-38 4 54-55 22 28 32 39 4 56-5823 29 33-34 40-41 4 59-61 24 30-31 35-36 42-44 4 62-24 25 32 37-38 45-464 65-67 26 33-35 39-41 47-49 4 68-84 27 36-52 42-64 50-75 ¹Severity ofDepression. 0 = None, 1 = Mild, 2 = Moderate, 3 = Severe, 4 = VerySevere.

QIDS-SR16 IDS-SR30 HAM-D24 HAM-D21 HAM-D17 0 0-3 0-1 0-1  0 1 4-5  2  21-2 2  6 3-4  3  3 3 7-8  5  4  4 4  9-11 6-7 5-6 5-6 5 12-13 8-9 7-8  76 14-16 10-11  9  8 7 17-18 12 10  9-10 8 19-21 13-14 11-12 11 9 22-2315-16 13 12 10 24-25 17-18 14-15 13 11 26-28 19 16 14-15 12 29-30 20-2117 16 13 31-33 22-23 18-19 17 14 34-36 24-25 20-21 18-19 15 37-38 26 2218-19 16 39-40 27-28 23 20 17 41-43 29-30 24-25 21-22 18 44-45 31-32 2623 19 46-47 33 27 24 20 48 34 28 25 21 49-53 35-38 29-31 26-27 22 54-5539 32 28 23 56-58 40-41 33-34 29 24 59-61 42-44 35-36 30-31 25 62-2445-46 37-38 32 26 65-67 47-49 39-41 33-35 27 68-84 50-75 42-64 36-52

IDS-SR30 QIDS-SR16 HAM-D24 HAM-D21 HAM-D17 0-2 0  0  0  0  3 0  1  1  14-5 1 2-3  2  2  6 2  4  3  3  7 3  5  4  3  8 3  5  4  4  9 4  6  5  510 4  7  6  5 11 4  7  6  6 12 5  8  7  6 13 5  9  7  7 14 6  9  8  7 156 10  9  8 16 6 11  9  9 17 7 12 10  9 18 7 12 10 10 19 8 13 11 10 20 814 12 11 21 8 15 12 11 22 9 15 13 12 23 9 16 13 12 24 10 17 14 13 25 1017 15 13 26 11 18 15 14 27 11 19 16 14 28 11 20 16 15 29 12 20 17 15 3012 21 17 16 31 13 22 18 16 32 13 22 19 17 33 13 23 19 17 34 14 24 20 1835 14 25 20 19 36 14 25 21 19 37-38 15 26 22 20 39-40 16 27-28 23 20 4117 29 24 21 42-43 17 30 25 22 44-45 18 31-32 26 23 46-47 19 33 27 24 4820 34 28 25 49-50 21 35 29 26 51-52 21 36-37 30 26 53 21 38 31 27 54-5522 39 32 28 56-57 23 40 33 29 58 23 41 34 29 59 24 42-43 35 30 60-61 2444 36 31 62 25 45 37 32 63-64 25 46 38 33 65 26 47 39 33 66 26 48 40 3467 26 49 41 35 68 27 50 42 35 69-70 27 51 43 36 71 27 52 44 37 72 2753-54 45 38 73-74 27 55 46 39 75-76 27 56 47-48 40 77-78 27 57-58 49-5042-43 79-82 27 59-62 51-54 44-48 83-84 27 63-75 55-64 49-52

In some embodiments, the combination of dextromethorphan and bupropionis a novel and oral NMDA receptor antagonist with multimodal activityfor the treatment of central nervous system (CNS) disorders. Thedextromethorphan is a non-competitive N-methyl-D-aspartate (NMDA)receptor antagonist, also known as a glutamate receptor modulator, whichis a novel mechanism of action that works differently than currentlyavailable therapies for depression.

The dextromethorphan is also a sigma-1 receptor agonist, nicotinicacetylcholine receptor antagonist, and inhibitor of the serotonin andnorepinephrine transporters. The bupropion can increase thebioavailability of dextromethorphan, and is a norepinephrine anddopamine reuptake inhibitor, and a nicotinic acetylcholine receptorantagonist. Both dextromethorphan and bupropion are nicotinicacetylcholine receptor antagonists, a mechanism that is relevant tonicotine dependence. Thus, the combination of dextromethorphan andbupropion provides a potentially new mechanism of action for smokingcessation treatment.

In some embodiments, the combination of dextromethorphan and bupropionmay be used to treat nicotine addiction. In some embodiments, thecombination of dextromethorphan and bupropion may be administered oncedaily or twice daily to a human being. In some embodiments, thecombination of dextromethorphan and bupropion may be administered twicedaily to a human being. In some embodiments, the combination ofdextromethorphan and bupropion may be administered once daily or twicedaily to a human being for at least 1 week, at least 2 weeks, at least 3weeks, at least 4 weeks, at least 5 weeks, at least 6 weeks, at least 1month, at least 2 months, at least 3 months, at least 4 months, at least5 months, at least 6-months, about 6-12 months, about 1 year, about 2years or longer. In some embodiments, the combination ofdextromethorphan and bupropion may be administered twice daily to ahuman being for at least 1 week, at least 2 weeks, at least 3 weeks, orlonger.

In some embodiments, the smoker may be, or may be selected for being, anad-lib smoker. In some embodiments, the smoker may, or may be selectedfor, smoking 10 or more cigarettes daily on average, such as about 10,about 10-15, about 10-17, about 10-20, about 11, about 12, about 13,about 14, about 15, about 16, about 17, about 18, about 19, about 20,about 20-25, about 25-30, about 30-40, about 40-50 cigarettes, or more,before administration of the combination of dextromethorphan andbupropion.

In some embodiments, the combination of dextromethorphan and bupropionmay be used to treat nicotine addiction, and the combination containsabout 30-100 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about60-70 mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 35 mg,about 35 mg, about 55 mg, about 65 mg, about 75 mg, about 85 mg, orabout 95 mg of dextromethorphan in a free base form or a salt form. Insome embodiments, the dextromethorphan is in an HBr salt form.

In some embodiments, the combination of dextromethorphan and bupropionmay be used to treat nicotine addiction, wherein the combinationcontains about 100-200 mg, about 100-150 mg, about 150-200 mg, about100-110 mg, about 110-120 mg, about 120-130 mg, about 130-140 mg, about140-150 mg, about 150-160 mg, about 160-170 mg, about 170-180 mg, about180-190 mg, about 190-200 mg, about 105 mg, about 115 mg, about 125 mg,about 135 mg, about 145 mg, about 150 mg, about 155-165 mg, about165-175 mg, about 175-185 mg, or about 185-195 mg of bupropion in a freebase form or a salt form. In some embodiments, the bupropion is in anHCl salt form.

In some embodiments, administration of the combination ofdextromethorphan and bupropion to human beings results in the reductionof smoking intensity as measured using the number of cigarettes smokedper day, assessed via daily smoking diaries.

The treatment with the combination of dextromethorphan and bupropion tohuman beings results in at least 5%, at least 10%, at least 15%, atleast 20%, at least 25%, about 5-10%, about 10-15%, about 15-20%, about20-25%, about 25-30%, 10-20%, about 20-30%, about 30-40%, about 40-50%,about 50-60%, about 60-80%, about 80-100%, about 20%, about 25% greater,about 30%, or about 50% reduction in the average number of cigarettessmoked per day as compared to bupropion alone over a period of time,such as 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 7 weeks, 8weeks, 9 weeks, 10 weeks, 11 weeks, 12 weeks, 3 months, 4 months, 6months, or longer.

The treatment with the combination of dextromethorphan and bupropion tohuman beings results in average reduction of at least 1, at least 2, atleast 3, at least 4, at least 5, at least 6, at least 7, at least 8, atleast 9, at least 10, at least 15, at least 20, about 8-9, about 8-10,about 10-15, about 15-20, about 25, or more cigarettes per day.

The treatment with the combination of dextromethorphan and bupropion tohuman beings results in a greater proportion of smokers, such as atleast 30%, at least 35%, at least 40%, at least 45%, at least 50%, atleast 55%, at least 60%, at least 65%, at least 70%, about 35%, about50%, about 60%, about 60-80%, about 80-90%, about 90-100%, whoexperience a more than 50% reduction in expired carbon monoxide levels,a biochemical marker of smoking intensity, as compared to those treatedwith bupropion alone.

The treatment with the combination of dextromethorphan and bupropion tohuman beings results in at least 1, or about 1-2 cigarettes fewer on theday of administration and at least 1, at least 2, about 1-2, or about2-3 cigarettes fewer on the following day as compared to those whomissed one or both doses of the combination of dextromethorphan andbupropion.

The treatment of smoking cessation with the combination ofdextromethorphan and bupropion to human beings results in the magnitudeof improvement over bupropion alone that is similar to the improvementover placebo reported for the approved smoking cessation treatmentvarenicline in studies with a similar design.

In some embodiments, an enhanced bioavailability of dextromethorphan, ora combination of dextromethorphan and an antidepressant such asbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, may be used as an adjunctive therapy for treatment of anycondition recited herein, including TRD. For example, the adjunctivetherapy could be used in combination with another antidepressant, suchas bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, clomipramine, doxepin, fluoxetine, mianserin,imipramine, 2-chloroimipramine, amitriptyline, amoxapine, desipramine,protriptyline, trimipramine, nortriptyline, maprotiline, phenelzine,isocarboxazid, tranylcypromine, paroxetine, trazodone, citalopram,sertraline, aryloxy indanamine, benactyzine, escitalopram, fluvoxamine,venlafaxine, desvenlafaxine, duloxetine, mirtazapine, nefazodone,selegiline, sibutramine, milnacipran, tesofensine, brasofensine,moclobemide, rasagiline, nialamide, iproniazid, iproclozide, toloxatone,butriptyline, dosulepin, dibenzepin, iprindole, lofepramine, opipramol,norfluoxetine, dapoxetine, ketamine, etc., or a metabolite or prodrug ofany of these compounds, or a pharmaceutically acceptable salt of any ofthese compounds.

In some embodiments, TRD may be treated by enhanced bioavailability orplasma levels of dextromethorphan, or by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds and may result in areduction of depressive symptoms of at least about 5%, at least about10%, at least about 20%, at least about 30%, at least about 40%, atleast about 50%, at least about 60%, at least about 70%, at least about80%, at least about 90%, up to about 100%, or any other reduction in arange bounded by any of these values.

Psychiatric disorders that may be treated by enhanced plasma levels ofdextromethorphan such as those achieved by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, include, but are notlimited to, anxiety disorders, including but not limited to, phobias,generalized anxiety disorder, social anxiety disorder, panic disorder,agoraphobia, obsessive-compulsive disorder, and post-traumatic stressdisorder (PTSD); mania, manic depressive illness, hypomania, unipolardepression, depression, stress disorders, somatoform disorders,personality disorders, psychosis, schizophrenia, delusional disorder,schizoaffective disorder, schizotypy, aggression, aggression inAlzheimer's disease, agitation, and agitation in Alzheimer's disease.

Agitation in Alzheimer's disease occurs as the disease progresses.Agitation may present itself as inappropriate verbal, emotional, and/orphysical behaviors. Inappropriate behaviors may include, but are notlimited to, incoherent babbling, inappropriate emotional response,demands for attention, threats, irritability, frustration, screaming,repetitive questions, mood swings, cursing, abusive language, physicaloutbursts, emotional distress, restlessness, shredding, sleepingdisturbances, delusions, hallucinations, pacing, wandering, searching,rummaging, repetitive body motions, hoarding, shadowing, hitting,scratching, biting, combativeness, hyperactivity, and/or kicking.

In some embodiments, agitation in Alzheimer's disease may be treated byenhanced plasma levels of dextromethorphan or by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds and may result in areduction of agitation-related symptoms of at least about 5%, at leastabout 10%, at least about 20%, at least about 30%, at least about 40%,at least about 50%, at least about 60%, at least about 70%, at leastabout 80%, at least about 90%, up to about 100%, or any other reductionin a range bounded by any of these values.

Alzheimer's disease (AD) is a progressive neurodegenerative disordercharacterized by cognitive decline, and behavioral and psychologicalsymptoms including agitation. AD is the most common form of dementia andafflicts an estimated 6 million individuals in the United States, anumber that is anticipated to increase to approximately 14 million by2050. Agitation is reported in up to 70% of patients with AD and ischaracterized by emotional distress, aggressive behaviors, disruptiveirritability, and disinhibition. Managing agitation is a priority in AD.Agitation in patients with AD has been associated with increasedcaregiver burden, decreased functioning, accelerated cognitive decline,earlier nursing home placement, and increased mortality. There arecurrently no therapies approved by the FDA for the treatment ofagitation in patients with AD.

Measures of treatment effect that may be improved by treatment withenhanced bioavailability or plasma levels of dextromethorphan, or by acombination of dextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, Neuropsychiatric Inventory-Clinician (NPI-C) rating scale,overall and all domains; Neuropsychiatric Inventory-Clinician (NPI-C)rating scale Agitation domain; Cohen-Mansfield Agitation Inventory(CMAI); Cornell Scale for Depression in Dementia (CSDD);Neuropsychiatric Inventory (NPI Agitation/Aggression Domain); CocomitantMedications (Frequency of using concomitant medications); Alzheimer'sDisease Cooperative Study—Activities of Daily Living Inventory(ADCS-ADL); Neuropsychiatric Inventory (NPI) Individual Domains and NPITotal Scores (range 0-144), including NPI-C Apathy domain, NPIAgitation/Aggression Caregiver Distress, Modified Alzheimer's DiseaseCooperative Study-Clinical Global Impression of Change Agitation(mADCS-CGIC Agitation), Patient Global Impression of Change (PGIC)(rated by caregiver), Dementia Quality of Life (DEMQOL), Quality ofLife-Alzheimer's disease measure (QoL-AD), Zarit Burden Scale, ResourceUtilization in Dementia (RUD), Alzheimer's Disease AssessmentScale-Cognitive Subscale (ADAS-Cog), Mini-mental State Examination(MMSE), Caregiver Strain Index (CSI), Individual Domain of theNeuropsychiatric Inventory (NPI), Total Neuropsychiatric Inventory (NPI)Score, Neuropsychiatric Inventory (Agitation/Aggression Domain of NPI),Neuropsychiatric Inventory (Caregiver Distress for NPI Domains), etc.

Substance addiction abuse that may be treated by enhancedbioavailability or plasma levels of dextromethorphan or by a combinationof dextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, includes, but is notlimited to, drug dependence, addiction to cocaine, psychostimulants(e.g., crack, cocaine, speed, meth), nicotine, alcohol, opioids,anxiolytic and hypnotic drugs, cannabis (marijuana), amphetamines,hallucinogens, phencyclidine, volatile solvents, and volatile nitrites.Nicotine addiction includes nicotine addiction of all known forms, suchas smoking cigarettes, cigars and/or pipes, and addiction to chewingtobacco.

Cerebral function disorders that may be treated by enhancedbioavailability or plasma levels of dextromethorphan, or by acombination of dextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, disorders involving intellectual deficits such as seniledementia, Alzheimer's type dementia, memory loss, amnesia/amnesticsyndrome, epilepsy, disturbances of consciousness, coma, lowering ofattention, speech disorders, voice spasms, Parkinson's disease,Lennox-Gastaut syndrome, autism, hyperkinetic syndrome, andschizophrenia. Cerebral function disorders also include disorders causedby cerebrovascular diseases including, but not limited to, stroke,cerebral infarction, cerebral bleeding, cerebral arteriosclerosis,cerebral venous thrombosis, head injuries, and the like where symptomsinclude disturbance of consciousness, senile dementia, coma, lowering ofattention, and speech disorders.

Movement disorders that may be treated by enhanced bioavailability orplasma levels of dextromethorphan, or by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, akathisia, akinesia, associated movements, athetosis,ataxia, ballismus, hemiballismus, bradykinesia, cerebral palsy, chorea,Huntington's disease, rheumatic chorea, Sydenham's chorea, dyskinesia,tardive dyskinesia, dystonia, blepharospasm, spasmodic torticollis,dopamine-responsive dystonia, Parkinson's disease, restless legssyndrome (RLS), tremor, essential tremor, and Tourette's syndrome, andWilson's disease.

Dementias that may be treated by enhanced bioavailability or plasmalevels of dextromethorphan, or by a combination of dextromethorphan andan antidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds include, but are not limited to,Alzheimer's disease, Parkinson's disease, vascular dementia, dementiawith Lewy bodies, mixed dementia, fronto-temporal dementia,Creutzfeldt-Jakob disease, normal pressure hydrocephalus, Huntington'sdisease, Wernicke-Korsakoff Syndrome, and Pick's disease.

Motor neuron diseases that may be treated by enhanced bioavailability orplasma levels of dextromethorphan, or by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, amyotrophic lateral sclerosis (ALS), progressive bulbarpalsy, primary lateral sclerosis (PLS), progressive muscular atrophy,post-polio syndrome (PPS), spinal muscular atrophy (SMA), spinal motoratrophies, Tay-Sach's disease, Sandoff disease, and hereditary spasticparaplegia.

Neurodegenerative diseases that may be treated by enhancedbioavailability or plasma levels of dextromethorphan, or by acombination of dextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, Alzheimer's disease, prion-related diseases, cerebellarataxia, spinocerebellar ataxia (SCA), spinal muscular atrophy (SMA),bulbar muscular atrophy, Friedrich's ataxia, Huntington's disease, Lewybody disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS orLou Gehrig's disease), multiple sclerosis (MS), multiple system atrophy,Shy-Drager syndrome, corticobasal degeneration, progressive supranuclearpalsy, Wilson's disease, Menkes disease, adrenoleukodystrophy, cerebralautosomal dominant arteriopathy with subcortical infarcts andleukoencephalopathy (CADASIL), muscular dystrophies, Charcot-Marie-Toothdisease (CMT), familial spastic paraparesis, neurofibromatosis,olivopontine cerebellar atrophy or degeneration, striatonigraldegeneration, Guillain-Barre syndrome, and spastic paraplesia.

Seizure disorders that may be treated by enhanced bioavailability orplasma levels of dextromethorphan, or by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, epileptic seizures, nonepileptic seizures, epilepsy, febrileseizures; partial seizures including, but not limited to, simple partialseizures, Jacksonian seizures, complex partial seizures, and epilepsiapartialis continua; generalized seizures including, but not limited to,generalized tonic-clonic seizures, absence seizures, atonic seizures,myoclonic seizures, juvenile myoclonic seizures, and infantile spasms;and status epilepticus.

Types of headaches that may be treated by enhanced bioavailability orplasma levels of dextromethorphan, or by a combination ofdextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, but are notlimited to, migraine, tension, and cluster headaches.

Other neurological disorders that may be treated by enhancedbioavailability or plasma levels of dextromethorphan, or by acombination of dextromethorphan and an antidepressant such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds include, Rett Syndrome,autism, tinnitus, disturbances of consciousness disorders, sexualdysfunction, intractable coughing, narcolepsy, cataplexy; voicedisorders due to uncontrolled laryngeal muscle spasms, including, butnot limited to, abductor spasmodic dysphonia, adductor spasmodicdysphonia, muscular tension dysphonia, and vocal tremor; diabeticneuropathy, chemotherapy-induced neurotoxicity, such as methotrexateneurotoxicity; incontinence including, but not limited, stress urinaryincontinence, urge urinary incontinence, and fecal incontinence; anderectile dysfunction.

In some embodiments, a combination of dextromethorphan and anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, may be used to treat pain, jointpain, pain associated with sickle cell disease, pseudobulbar affect,depression (including treatment resistant depression), disorders relatedto memory and cognition, schizophrenia, Parkinson's disease, amyotrophiclateral sclerosis (ALS), Rhett's syndrome, seizures, cough (includingchronic cough), etc.

In some embodiments, a combination of dextromethorphan and anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds may be used to treat treatmentrefractory depression.

In some embodiments, a combination of dextromethorphan and anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds may be used to treat allodynia.

In some embodiments, a combination of dextromethorphan and anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds may be used to treat treatmentrefractory hyperalgesia.

In some embodiments, a combination of dextromethorphan and anantidepressant such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds may be used to treat dermatitis.

Pain relieving properties of dextromethorphan may be enhanced by amethod comprising co-administering dextromethorphan and anantidepressant, such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, with dextromethorphan.

Pain relieving properties of bupropion may be enhanced by a methodcomprising co-administering dextromethorphan with bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds.

In some embodiments, ketamine or another NMDA receptor antagonist may beadministered with an antidepressant, such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds.

In some embodiments, dextromethorphan and quinidine may beco-administered with an antidepressant, such as bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds.

These methods may be used to treat, or provide relief to, any type ofpain including, but not limited to, musculoskeletal pain, neuropathicpain, cancer-related pain, acute pain, nociceptive pain, inflammatorypain, arthritis pain, complex regional pain syndrome, etc.

In some embodiments, co-administering dextromethorphan with bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds may be used to treat orreduce inflammation or inflammatory conditions, such as Crohn's disease,including pain associated with inflammation.

In some embodiments, co-administering dextromethorphan with bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds may be used to treatpsoriasis, cancer, viral infection, or as an adjuvant treatment formultiple myeloma.

Examples of musculoskeletal pain include low back pain (i.e. lumbosacralpain), primary dysmenorrhea, and arthritic pain, such as pain associatedwith rheumatoid arthritis, juvenile rheumatoid arthritis,osteoarthritis, axial spondyloarthritis including ankylosingspondylitis, pain associated with vertebral crush fractures, fibrousdysplasia, osteogenesis imperfecta, Paget's disease of bone, transientosteoporosis, and transient osteoporosis of the hip, etc.

In some embodiments, a combination of dextromethorphan and anantidepressant, such as bupropion, may be administered orally to relievemusculoskeletal pain including low back pain, and pain associated withrheumatoid arthritis, juvenile rheumatoid arthritis, osteoarthritis,erosive osteoarthritis, sero-negative (non-rheumatoid) arthropathies,non-articular rheumatism, peri-articular disorders, axialspondyloarthritis including ankylosing spondylitis, Paget's disease,fibrous dysplasia, SAPHO syndrome, transient osteoarthritis of the hip,vertebral crush fractures, osteoporosis, etc.

In some embodiments, a combination of dextromethorphan and anantidepressant, such as bupropion, may be administered to relieveinflammatory pain including musculoskeletal pain, arthritis pain, andcomplex regional pain syndrome.

Arthritis refers to inflammatory joint diseases that can be associatedwith pain. Examples of arthritis pain include pain associated withosteoarthritis, erosive osteoarthritis, rheumatoid arthritis, juvenilerheumatoid arthritis, sero-negative (non-rheumatoid) arthropathies,non-articular rheumatism, peri-articular disorders, neuropathicarthropathies including Charcot's foot, axial spondyloarthritisincluding ankylosing spondylitis, and SAPHO syndrome.

In some embodiments, a combination of dextromethorphan and anantidepressant, such as bupropion, is used to treat chronicmusculoskeletal pain.

In some embodiments, a combination of dextromethorphan and anantidepressant, such as bupropion, may be administered to relievecomplex regional pain syndrome, such as complex regional pain syndrometype I (CRPS-I), complex regional pain syndrome type II (CRPS-II),CRPS-NOS, or another type of CRPS. CRPS is a type of inflammatory pain.CRPS can also have a neuropathic component. Complex regional painsyndrome is a debilitating pain syndrome. It is characterized by severepain in a limb that can be accompanied by edema, and autonomic, motorand sensory changes.

In some embodiments, a combination of dextromethorphan and anantidepressant, such as bupropion, may be administered orally to relieveneuropathic pain.

Examples of neuropathic pain include diabetic peripheral neuropathy,post-herpetic neuralgia, trigeminal neuralgia, monoradiculopathies,phantom limb pain, central pain, etc. Other causes of neuropathic paininclude cancer-related pain, lumbar nerve root compression, spinal cordinjury, post-stroke pain, central multiple sclerosis pain,HIV-associated neuropathy, and radio- or chemo-therapy associatedneuropathy, etc.

In some embodiments, a combination of dextromethorphan and anantidepressant, such as bupropion, may be administered to relievefibromyalgia.

The term “treating” or “treatment” includes the diagnosis, cure,mitigation, treatment, or prevention of disease in man or other animals,or any activity that otherwise affects the structure or any function ofthe body of man or other animals.

Any antidepressant may be used in combination with dextromethorphan toimprove the therapeutic properties of dextromethorphan. Dextromethorphanand the antidepressant compound may be administered in separatecompositions or dosage forms or may be administered in a singlecomposition or dosage form comprising both.

A quinidine may be co-administered with dextromethorphan to provideenhanced plasma levels of dextromethorphan. For a combination of aquinidine and a dextromethorphan (including deuterium-modifieddextromethorphan, e.g. d6-dextromethorphan, and non-deuterium modifieddextromethorphan), a daily dose of about 1-1,000 mg, 1-10 mg, 10 mg,about 5 mg, about 4.5, about 1-3 mg, about 2-4 mg, about 3-5 mg, about4-6 mg, about 5-7 mg, about 6-8 mg, about 7-9 mg, about 8-10 mg, about9-11 mg, about 10-12 mg, about 4.5-5 mg, 20 mg, 30 mg, 30-100 mg, about40 mg, about 50 mg, about 60 mg, about 70 mg, about 80 mg, about 90 mg,about 10-30 mg, about 30-50 mg, about 50-70 mg, about 10-90 mg of thequinidine, or any dose in a range bounded by any of these values.

Antidepressant compounds that can be co-administered withdextromethorphan include, but are not limited to, bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion,clomipramine, doxepin, fluoxetine, mianserin, imipramine,2-chloroimipramine, amitriptyline, amoxapine, desipramine,protriptyline, trimipramine, nortriptyline, maprotiline, phenelzine,isocarboxazid, tranylcypromine, paroxetine, trazodone, citalopram,sertraline, aryloxy indanamine, benactyzine, escitalopram, fluvoxamine,venlafaxine, desvenlafaxine, duloxetine, mirtazapine, nefazodone,selegiline, sibutramine, milnacipran, tesofensine, brasofensine,moclobemide, rasagiline, nialamide, iproniazid, iproclozide, toloxatone,butriptyline, dosulepin, dibenzepin, iprindole, lofepramine, opipramol,norfluoxetine, dapoxetine, ketamine, etc., or a metabolite or prodrug ofany of these compounds, or a pharmaceutically acceptable salt of any ofthese compounds.

For a combination of a ketamine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.01-0.2mg, about 0.2-0.4 mg, about 0.4-0.6 mg, about 0.6-0.8 mg, about 0.8-1mg, about 1-1.2 mg, about 1.2-1.4 mg, about 1.4-1.6 mg, about 1.6-1.8mg, about 1.8-2 mg, about 2-2.2 mg, about 2.2-2.4 mg, about 2.4-2.6 mg,about 2.6-2.8 mg, about 2.8-3 mg, about 3-3.2 mg, about 3.2-3.4 mg,about 3.4-3.6 mg, about 3.6-3.8 mg, about 3.8-4 mg, about 3.9-4.1 mg,about 4-4.2 mg, about 0.2-0.4 mg, about 0.2-0.6 mg, about 0.2-0.8 mg,about 0.2-1 mg, about 0.2-1.2 mg, about 0.2-1.4 mg, about 0.2-1.6 mg,about 0.2-1.8 mg, about 0.2-2.0 mg, 0.2-2.5 mg, about 0.2-3.0 mg, about0.2-3.5 mg, about 0.2-4.0 mg, about 5-10 mg, about 10-15 mg, about 15-20mg, about 20-25 mg, about 25-30 mg, about 30-40 mg, about 40-50 mg,about 50-60 mg, about 60-70 mg, about 70-80 mg, about 80-90 mg, about90-100 mg, about 100-120 mg, about 120-140 mg, about 140-150 mg, about150-160 mg, about 160-180 mg, about 180-200 mg, about 200-220 mg, about220-240, about 10-500 mg, about 50-400 mg, about 50-300 mg, about100-250 mg, about 1-10 mg, about 10-200 mg, about 10-150 mg, about10-100 mg, about 10-180 mg, about 10-160 mg, about 10-140 mg, about10-120 mg, about 10-100 mg, about 10-20 mg, about 20-30 mg, about 30-40mg, about 40-50 mg, about 50-60 mg, about 60-70 mg, about 70-80 mg,about 80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg,about 140-160 mg, about 160-180 mg, about 180-200 mg, about 200-220 mg,about 220-240, about 240-250 mg, about 250-260 mg, about 260-280 mg,about 280-300 mg, about 300-350 mg, about 350-400 mg, about 25 mg, about50 mg, about 100 mg, about 250 mg, of the ketamine, or any dose in arange bounded by any of these values, may be administered.

For a combination of a tesofensine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.2mg, about 0.1-0.3 mg, about 0.1-0.4 mg, about 0.1-0.5 mg, about 0.1-0.6mg, about 0.1-0.7 mg, about 0.1-0.8 mg, about 0.1-0.9 mg, about 0.1-0.1mg, about 0.1-0.12 mg, 0.01-0.2 mg, about 0.1-0.3 mg, about 0.2-0.4 mg,about 0.3-0.5 mg, about 0.4-0.6 mg, about 0.5-0.7 mg, about 0.6-0.8 mg,about 0.7-0.9 mg, about 0.8-1 mg, about 0.9-1.1 mg, of the tesofensine,or any dose in a range bounded by any of these values, may beadministered.

For a combination of a brasofensine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.01-0.2mg, about 0.2-0.4 mg, about 0.4-0.6 mg, about 0.6-0.8 mg, about 0.8-1mg, about 1-1.2 mg, about 1.2-1.4 mg, about 1.4-1.6 mg, about 1.6-1.8mg, about 1.8-2 mg, about 2-2.2 mg, about 2.2-2.4 mg, about 2.4-2.6 mg,about 2.6-2.8 mg, about 2.8-3 mg, about 3-3.2 mg, about 3.2-3.4 mg,about 3.4-3.6 mg, about 3.6-3.8 mg, about 3.8-4 mg, about 3.9-4.1 mg,about 4-4.2 mg, about 0.2-0.4 mg, about 0.2-0.6 mg, about 0.2-0.8 mg,about 0.2-1 mg, about 0.2-1.2 mg, about 0.2-1.4 mg, about 0.2-1.6 mg,about 0.2-1.8 mg, about 0.2-2.0 mg, 0.2-2.5 mg, about 0.2-3.0 mg, about0.2-3.5 mg, about 0.2-4.0 mg, of the brasofensine, or any dose in arange bounded by any of these values, may be administered.

For a combination of a clomipramine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 10-500mg, about 50-400 mg, about 50-300 mg, about 100-250 mg, about 1-10 mg,about 10-200 mg, about 10-150 mg, about 10-100 mg, about 10-180 mg,about 10-160 mg, about 10-140 mg, about 10-120 mg, about 10-100 mg,about 10-20 mg, about 20-30 mg, about 30-40 mg, about 40-50 mg, about50-60 mg, about 60-70 mg, about 70-80 mg, about 80-90 mg, about 90-100mg, about 100-120 mg, about 120-140 mg, about 140-160 mg, about 160-180mg, about 180-200 mg, about 200-220 mg, about 220-240, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-350 mg,about 350-400 mg, about 25 mg, about 50 mg, about 100 mg, about 250 mg,of the clomipramine, or any dose in a range bounded by any of thesevalues, may be administered.

For a combination of a doxepin and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-500mg, about 1-10 mg, about 1-40 mg, about 1-30 mg, about 1-20 mg, about1-18 mg, about 1-16 mg, about 1-14 mg, about 1-12 mg, about 1-10 mg,about 10-150 mg, about 10-125 mg, about 10-100 mg, about 10-75 mg, about10-70 mg, about 10-60 mg, about 10-50 mg, about 10-40 mg, about 10-30mg, about 10-20 mg, about 20-30 mg, about 30-40 mg, about 40-50 mg,about 50-60 mg, about 60-70 mg, about 70-80 mg, about 80-90 mg, about90-100 mg, about 100-120 mg, about 120-140 mg, about 140-160 mg, about160-180 mg, about 180-200 mg, about 200-220 mg, about 220-240, about240-250 mg, about 250-260 mg, about 260-280 mg, about 280-300 mg, about300-320 mg, about 320-350 mg, about 350-400 mg, about 400-500 mg, about25 mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about 250mg, about 300 mg, of the doxepin, or any dose in a range bounded by anyof these values, may be administered.

For a combination of a fluoxetine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of a daily doseof about 1-10 mg, about 5-15 mg, about 10-20 mg, about 20-30 mg, about30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70 mg, about 70-80mg, about 80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg,about 140-160 mg, about 160-180 mg, about 180-200 mg, about 10 mg, about20 mg, about 60 mg, about 100 mg, about 150 mg, of the fluoxetine, orany dose in a range bounded by any of these values, may be administered.

For a combination of a mianserin and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-300mg, about 1-90 mg, about 1-60 mg, about 1-30 mg, about 1-25 mg, about1-20 mg, about 1-15 mg, about 1-10 mg, about 10-20 mg, about 20-30 mg,about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70 mg, about70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg, about120-140 mg, about 140-160 mg, about 160-180 mg, about 180-200 mg, about30 mg, about 60 mg, about 90 mg, about 120 mg, about 150 mg, of themianserin, or any dose in a range bounded by any of these values, may beadministered.

For a combination of a imipramine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 5-150 mg, about 5-125 mg, about 5-100 mg, about 5-75 mg, about5-60 mg, about 5-50 mg, about 5-40 mg, about 5-30 mg, about 5-25 mg,about 5-20 mg, about 5-15 mg, about 10-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-160 mg, about 160-180 mg, about 180-200 mg,about 200-220 mg, about 220-240, about 240-250 mg, about 250-260 mg,about 260-280 mg, about 280-300 mg, about 300-320 mg, about 320-350 mg,about 350-400 mg, about 400-500 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, of theimipramine, or any dose in a range bounded by any of these values, maybe administered.

For a combination of a 2-chloroimipramine and a dextromethorphan(including deuterium-modified dextromethorphan, e.g.d6-dextromethorphan, and non-deuterium modified dextromethorphan), adaily dose of about 0.1-0.25 mg, about 0.25-0.5 mg, about 0.5-0.75 mg,about 0.75-1 mg, about 1-5 mg, about 5-10 mg, about 10-15 mg, about15-20 mg, about 20-25 mg, about 25-30 mg, about 30-40 mg, about 40-50mg, about 50-60 mg, about 60-70 mg, about 70-80 mg, about 80-90 mg,about 90-100 mg, about 100-120 mg, about 120-140 mg, about 140-150 mg,about 150-160 mg, about 160-180 mg, about 180-200 mg, about 200-220 mg,about 220-240, about 240-250 mg, about 250-260 mg, about 260-280 mg,about 280-300 mg, about 300-320 mg, about 320-350 mg, about 350-400 mg,about 400-450 mg, about 450-500 mg, about 500-550 mg, about 550-600 mg,about 600-650 mg, about 650-700 mg, about 700-800 mg, about 800-1000 mg,about 25 mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about250 mg, about 300 mg, about 400 mg, about 600 mg, of the about2-chloroimipramine, or any dose in a range bounded by any of thesevalues, may be administered.

For a combination of an amitriptyline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 5-100 mg, about 5-70 mg, about 5-60 mg, about 5-50 mg, about 5-40mg, about 5-35 mg, about 5-30 mg, about 5-25 mg, about 5-20 mg, about10-20 mg, about 20-30 mg, about 30-40 mg, about 40-50 mg, about 50-60mg, about 60-70 mg, about 70-80 mg, about 80-90 mg, about 90-100 mg,about 100-120 mg, about 120-140 mg, about 140-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-500 mg, about 10 mg, about25 mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about 250mg, about 300 mg, of the amitriptyline, or any dose in a range boundedby any of these values, may be administered.

For a combination of an amoxapine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 10-20 mg, about 10-300 mg, about 10-250 mg, about 10-200 mg, about10-150 mg, about 10-120 mg, about 10-100 mg, about 10-80 mg, about 10-60mg, about 10-40 mg, about 20-25 mg, about 25-30 mg, about 30-40 mg,about 40-50 mg, about 50-60 mg, about 60-70 mg, about 70-80 mg, about80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg, about140-160 mg, about 160-180 mg, about 180-200 mg, about 200-220 mg, about220-240, about 240-250 mg, about 250-260 mg, about 260-280 mg, about280-300 mg, about 300-320 mg, about 320-350 mg, about 350-400 mg, about400-500 mg, about 500-600 mg, about 600-700 mg, about 700-800 mg, about25 mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about 250mg, about 300 mg, about 400 mg, of the amoxapine, or any dose in a rangebounded by any of these values, may be administered.

For a combination of a desipramine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 1-15 mg, about 10-20 mg, about 10-25 mg, about 10-30 mg, about10-40 mg, about 10-50 mg, about 10-60 mg, about 10-70 mg, about 10-80mg, about 10-90 mg, about 10-100 mg, about 10-120 mg, about 10-140 mg,about 10-150 mg, about 10-180 mg, about 10-200 mg, about 20-30 mg, about20-40 mg, about 30-40 mg, about 40-50 mg, about 40-60 mg, about 50-60mg, about 60-70 mg, about 70-80 mg, about 80-90 mg, about 90-100 mg,about 90-110 mg, about 100-120 mg, about 120-140 mg, about 140-160 mg,about 160-180 mg, about 180-200 mg, about 180-220 mg, about 200-220 mg,about 220-240, about 240-250 mg, about 250-260 mg, about 260-280 mg,about 280-300 mg, about 280-320 mg, about 300-350 mg, about 350-400 mg,about 100-200 mg, about 25-100 mg, about 25 mg, about 50 mg, about 100mg, about 200 mg, about 250 mg, of the desipramine, or any dose in arange bounded by any of these values, may be administered.

For a combination of a protriptyline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 5-100mg, about 2-5 mg, about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9mg, about 2-10 mg, about 2-11 mg, about 2-12 mg, about 2-13 mg, about2-14 mg, about 2-15 mg, about 2-20 mg, about 2-21 mg, about 2-22 mg,about 2-23 mg, about 2-24 mg, about 2-25 mg, about 2-26 mg, about 2-27mg, about 2-28 mg, about 2-29 mg, about 2-30 mg, about 2-35 mg, about2-40 mg, about 15-60 mg, about 1-5 mg, about 5-10 mg, about 10-15 mg,about 15-20 mg, about 20-25 mg, about 25-30 mg, about 30-35 mg, about35-40 mg, about 40-45 mg, about 45-50 mg, about 50-55 mg, about 55-60mg, about 60-65 mg, about 65-70 mg, about 70-80 mg, about 80-90 mg,about 90-100 mg, about 100-120 mg, about 120-140 mg, about 140-160 mg,about 160-180 mg, about 180-200 mg, about 10 mg, about 20 mg, about 30mg, about 60 mg, about 100 mg, about 150 mg, of the protriptyline, orany dose in a range bounded by any of these values, may be administered.

For a combination of a trimipramine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 20-300mg, about 1-10 mg, about 5-20 mg, about 5-25 mg, about 5-30 mg, about5-35 mg, about 5-40 mg, about 5-45 mg, about 5-50 mg, about 5-55 mg,about 5-60 mg, about 5-65 mg, about 5-70 mg, about 5-75 mg, about 5-100mg, about 5-125 mg, about 5-150 mg, about 10-20 mg, about 20-30 mg,about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70 mg, about70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg, about100-200 mg, about 120-140 mg, about 140-160 mg, about 160-180 mg, about180-200 mg, about 180-220 mg, about 200-220 mg, about 220-240 mg, about240-250 mg, about 250-260 mg, about 260-280 mg, about 280-300 mg, about300-320 mg, about 320-350 mg, about 350-400 mg, about 400-500 mg, about10 mg, about 25 mg, about 50 mg, about 75 mg, about 100 mg, about 150mg, about 250 mg, about 300 mg, of the trimipramine, or any dose in arange bounded by any of these values, may be administered.

For a combination of a nortriptyline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 5-10 mg, about 5-20 mg, about 5-25 mg, about 5-30 mg, about 5-35mg, about 5-40 mg, about 5-45 mg, about 5-50 mg, about 5-55 mg, about5-60 mg, about 5-65 mg, about 5-70 mg, about 5-75 mg, about 5-100 mg,about 5-125 mg, about 5-150 mg, about 10-15 mg, about 15-20 mg, about20-25 mg, about 20-30 mg, about 25-30 mg, about 30-35 mg, about 30-50mg, about 35-40 mg, about 40-45 mg, about 45-50 mg, about 50-150 mg,about 50-55 mg, about 55-60 mg, about 60-65 mg, about 65-70 mg, about70-80 mg, about 80-90 mg, about 80-120 mg, about 90-100 mg, about100-120 mg, about 120-140 mg, about 140-160 mg, about 160-180 mg, about180-200 mg, about 10 mg, about 20 mg, about 30 mg, about 60 mg, about100 mg, about 150 mg, of the nortriptyline, or any dose in a rangebounded by any of these values, may be administered.

For a combination of a maprotiline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 5-10 mg, about 5-20 mg, about 5-25 mg, about 5-30 mg, about 5-35mg, about 5-40 mg, about 5-45 mg, about 5-50 mg, about 5-55 mg, about5-60 mg, about 5-65 mg, about 5-70 mg, about 5-75 mg, about 5-100 mg,about 5-125 mg, about 5-150 mg, about 10-15 mg, about 10-250 mg, about10-75 mg, about 10-50 mg, about 15-20 mg, about 20-25 mg, about 25-30mg, about 30-35 mg, about 35-40 mg, about 40-45 mg, about 45-50 mg,about 50-55 mg, about 55-60 mg, about 60-65 mg, about 60-90 mg, about65-70 mg, about 70-75 mg, about 75-80 mg, about 80-85 mg, about 80-120mg, about 85-90 mg, about 90-100 mg, about 100-120 mg, about 100-150 mg,about 120-125 mg, about 125-140 mg, about 140-150 mg, about 150-160 mg,about 160-180 mg, about 180-200 mg, about 200-225 mg, about 210-240 mg,about 200-250 mg, about 10 mg, about 25 mg, about 30 mg, about 50 mg,about 75 mg, about 100 mg, about 150 mg, about 225 mg, of themaprotiline, or any dose in a range bounded by any of these values, maybe administered.

For a combination of a phenelzine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 5-10 mg, about 5-20 mg, about 5-25 mg, about 5-30 mg, about 5-35mg, about 5-40 mg, about 5-45 mg, about 5-50 mg, about 5-55 mg, about5-60 mg, about 5-65 mg, about 5-70 mg, about 5-75 mg, about 5-90 mg,about 10-15 mg, about 15-20 mg, about 20-25 mg, about 25-30 mg, about30-35 mg, about 35-40 mg, about 40-45 mg, about 40-50 mg, about 45-50mg, about 50-55 mg, about 50-70 mg, about 50-200 mg, about 55-60 mg,about 60-65 mg, about 60-90 mg, about 65-70 mg, about 70-80 mg, about80-90 mg, 80-120 mg, about 90-100 mg, about 100-120 mg, about 100-150mg, about 120-140 mg, about 140-160 mg, about 160-180 mg, about 180-200mg, about 10 mg, about 15 mg, about 30 mg, about 60 mg, about 100 mg,about 150 mg, of the phenelzine, or any dose in a range bounded by anyof these values, may be administered.

For a combination of a isocarboxazid and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 2-5 mg, about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9 mg,about 2-10 mg, about 2-11 mg, about 2-12 mg, about 2-13 mg, about 2-14mg, about 2-15 mg, about 2-16 mg, about 2-17 mg, about 2-18 mg, about2-19 mg, about 2-20 mg, about 2-21 mg, about 2-22 mg, about 2-23 mg,about 2-24 mg, about 2-25 mg, about 2-26 mg, about 2-27 mg, about 2-28mg, about 2-29 mg, about 2-30 mg, about 2-35 mg, about 2-40 mg, about2-45 mg, about 2-50 mg, about 2-55 mg, about 2-60 mg, about 5-10 mg,about 5-15 mg, about 10-15 mg, about 10-60 mg, about 15-20 mg, about20-25 mg, about 25-30 mg, about 30-35 mg, about 30-50 mg, about 35-40mg, about 40-45 mg, about 45-50 mg, about 50-55 mg, about 50-70 mg,about 55-60 mg, about 60-65 mg, about 65-70 mg, about 70-80 mg, about80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg, about140-160 mg, about 160-180 mg, about 180-200 mg, about 10 mg, about 15mg, about 30 mg, about 60 mg, about 100 mg, about 150 mg, of theisocarboxazid, or any dose in a range bounded by any of these values,may be administered.

For a combination of a tranylcypromine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 1-30 mg, about 1-25 mg, about 1-20 mg, about 2-5 mg, about 2-6 mg,about 2-7 mg, about 2-8 mg, about 2-9 mg, about 2-10 mg, about 2-11 mg,about 2-12 mg, about 2-13 mg, about 2-14 mg, about 2-15 mg, about 2-16mg, about 2-17 mg, about 2-18 mg, about 2-19 mg, about 2-20 mg, about2-21 mg, about 2-22 mg, about 2-23 mg, about 2-24 mg, about 2-25 mg,about 2-26 mg, about 2-27 mg, about 2-28 mg, about 2-29 mg, about 2-30mg, about 2-35 mg, about 2-40 mg, about 2-45 mg, about 2-50 mg, about2-55 mg, about 2-60 mg, about 5-10 mg, about 10-15 mg, about 15-20 mg,about 20-25 mg, about 25-30 mg, about 30-35 mg, about 35-40 mg, about40-45 mg, about 45-50 mg, about 50-55 mg, about 55-60 mg, about 60-65mg, about 65-70 mg, about 70-80 mg, about 80-90 mg, about 90-100 mg,about 100-120 mg, about 120-140 mg, about 140-160 mg, about 160-180 mg,about 180-200 mg, about 10 mg, about 15 mg, about 30 mg, about 60 mg,about 100 mg, about 150 mg, of the tranylcypromine, or any dose in arange bounded by any of these values, may be administered.

For a combination of a paroxetine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 1-50 mg, about 1-20 mg, about 1-15 mg, about 1-10 mg, about 2-5mg, about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9 mg, about 2-10mg, about 2-11 mg, about 2-12 mg, about 2-13 mg, about 2-14 mg, about2-15 mg, about 2-16 mg, about 2-17 mg, about 2-18 mg, about 2-19 mg,about 2-20 mg, about 2-30 mg, about 2-40 mg, about 2-50 mg, about 5-10mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about 25-30 mg,about 30-35 mg, about 35-40 mg, about 40-45 mg, about 45-50 mg, about50-55 mg, about 55-60 mg, about 60-65 mg, about 65-70 mg, about 70-80mg, about 80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg,about 140-160 mg, about 160-180 mg, about 180-200 mg, about 10 mg, about15 mg, about 20 mg, about 30 mg, about 60 mg, about 100 mg, about 150mg, of the paroxetine, or any dose in a range bounded by any of thesevalues, may be administered.

For a combination of a trazodone and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 10-20 mg, about 10-30 mg, about 10-40 mg, about 10-50 mg, about10-60 mg, about 10-70 mg, about 10-80 mg, about 10-90 mg, about 10-100mg, about 10-120 mg, about 10-140 mg, about 10-150 mg, about 10-180 mg,about 10-200 mg, about 10-250 mg, about 10-300 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 25 mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about250 mg, about 300 mg, about 400 mg, about 600 mg, of the trazodone, orany dose in a range bounded by any of these values, may be administered.

For a combination of a citalopram and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 1-20 mg, about 1-15 mg, about 1-10 mg, about 2-5 mg, about 2-6 mg,about 2-7 mg, about 2-8 mg, about 2-9 mg, about 2-10 mg, about 2-11 mg,about 2-12 mg, about 2-13 mg, about 2-14 mg, about 2-15 mg, about 2-20mg, about 2-25 mg, about 2-30 mg, about 2-35 mg, about 2-40 mg, about5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about 25-30 mg,about 30-35 mg, about 35-40 mg, about 40-45 mg, about 45-50 mg, about50-55 mg, about 55-60 mg, about 60-65 mg, about 65-70 mg, about 70-80mg, about 80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg,about 140-160 mg, about 160-180 mg, about 180-200 mg, about 10 mg, about15 mg, about 20 mg, about 30 mg, about 40 mg, about 60 mg, about 100 mg,about 150 mg, of the citalopram, or any dose in a range bounded by anyof these values, may be administered.

For a combination of a sertraline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 1-50 mg, about 1-45 mg, about 1-40 mg, about 1-30 mg, about 1-20mg, about 2-5 mg, about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9mg, about 2-10 mg, about 2-11 mg, about 2-12 mg, about 2-13 mg, about2-14 mg, about 2-15 mg, about 2-16 mg, about 2-17 mg, about 2-18 mg,about 2-19 mg, about 2-20 mg, about 2-21 mg, about 2-22 mg, about 2-23mg, about 2-24 mg, about 2-25 mg, about 2-26 mg, about 2-27 mg, about2-28 mg, about 2-29 mg, about 2-30 mg, about 2-35 mg, about 2-40 mg,about 2-45 mg, about 2-50 mg, about 5-10 mg, about 10-15 mg, about 15-20mg, about 20-25 mg, about 25-30 mg, about 30-35 mg, about 35-40 mg,about 40-45 mg, about 45-50 mg, about 50-55 mg, about 55-60 mg, about60-65 mg, about 65-70 mg, about 70-75 mg, about 75-80 mg, about 80-85mg, about 85-90 mg, about 90-100 mg, about 100-120 mg, about 120-125 mg,about 125-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-300 mg, about 10 mg, about 25 mg, about 30mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about 200 mg,about 225 mg, of sertraline, or any dose in a range bounded by any ofthese values, may be administered.

For a combination of an aryloxy indanamine and a dextromethorphan(including deuterium-modified dextromethorphan, e.g.d6-dextromethorphan, and non-deuterium modified dextromethorphan), adaily dose of about 0.1-0.25 mg, about 0.25-0.5 mg, about 0.5-0.75 mg,about 0.75-1 mg, about 1-5 mg, about 5-10 mg, about 10-15 mg, about15-20 mg, about 20-25 mg, about 25-30 mg, about 30-40 mg, about 40-50mg, about 50-60 mg, about 60-70 mg, about 70-80 mg, about 80-90 mg,about 90-100 mg, about 100-120 mg, about 120-140 mg, about 140-150 mg,about 150-160 mg, about 160-180 mg, about 180-200 mg, about 200-220 mg,about 220-240, about 240-250 mg, about 250-260 mg, about 260-280 mg,about 280-300 mg, about 300-320 mg, about 320-350 mg, about 350-400 mg,about 400-450 mg, about 450-500 mg, about 500-550 mg, about 550-600 mg,about 600-650 mg, about 650-700 mg, about 700-800 mg, about 800-1000 mg,about 25 mg, about 50 mg, about 75 mg, about 100 mg, about 150 mg, about250 mg, about 300 mg, about 400 mg, about 600 mg, of the aryloxyindanamine, or any dose in a range bounded by any of these values, maybe administered.

For a combination of a benactyzine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the benactyzine, or any dose in a range bounded byany of these values, may be administered.

For a combination of a escitalopram and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 2-5 mg, about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9 mg,about 2-10 mg, about 2-12 mg, about 2-14 mg, about 2-15 mg, about 2-20mg, about 5-10 mg, about 5-15 mg, about 10-15 mg, about 10-30 mg, about15-20 mg, about 15-30 mg, about 20-25 mg, about 25-30 mg, about 30-35mg, about 35-40 mg, about 40-45 mg, about 45-50 mg, about 50-55 mg,about 55-60 mg, about 60-65 mg, about 65-70 mg, about 70-80 mg, about80-90 mg, about 90-100 mg, about 100-200 mg, about 5 mg, about 10 mg,about 15 mg, about 20 mg, about 25 mg, about 30 mg, about 35 mg, about40 mg, about 50 mg, of the escitalopram, or any dose in a range boundedby any of these values, may be administered.

For a combination of a fluvoxamine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of 50-300 mg,1-10 mg, about 10-20 mg, about 10-30 mg, about 10-40 mg, about 10-50 mg,about 10-60 mg, about 10-70 mg, about 10-80 mg, about 10-90 mg, about10-100 mg, about 10-120 mg, about 10-140 mg, about 10-150 mg, about10-180 mg, about 10-200 mg, about 10-250 mg, about 10-300 mg, about20-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 90-110 mg,about 100-120 mg, about 120-140 mg, about 140-160 mg, about 160-180 mg,about 180-200 mg, about 180-220 mg, about 200-220 mg, about 220-240,about 240-250 mg, about 240-260 mg, about 250-260 mg, about 260-280 mg,about 280-300 mg, about 280-320 mg, about 300-320 mg, about 320-350 mg,about 350-400 mg, about 400-500 mg, about 10 mg, about 25 mg, about 50mg, about 75 mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg,of the fluvoxamine, or any dose in a range bounded by any of thesevalues, may be administered.

For a combination of a venlafaxine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 5-20 mg, about 5-25 mg, about 5-30 mg, about 5-35 mg, about 5-40mg, about 5-45 mg, about 5-50 mg, about 5-55 mg, about 5-60 mg, about5-65 mg, about 5-70 mg, about 5-75 mg, about 5-100 mg, about 5-125 mg,about 5-150 mg, about 10-20 mg, about 20-25 mg, about 25-30 mg, about30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70 mg, about 70-80mg, about 80-90 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg,about 140-150 mg, about 120-180 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 225, about 250 mg, about 375 mg,about 400 mg, about 600 mg, of the venlafaxine, or any dose in a rangebounded by any of these values, may be administered.

For a combination of a desvenlafaxine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 2-5 mg,about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9 mg, about 2-10 mg,about 2-11 mg, about 2-12 mg, about 2-13 mg, about 2-14 mg, about 2-15mg, about 2-20 mg, about 2-21 mg, about 2-22 mg, about 2-23 mg, about2-24 mg, about 2-25 mg, about 2-30 mg, about 2-35 mg, about 2-40 mg,about 2-45 mg, about 2-50 mg, about 2-75 mg, about 2-100 mg, about 1-5mg, about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about20-30 mg, about 25-30 mg, about 30-35 mg, about 35-40 mg, about 40-45mg, about 40-60 mg, about 45-50 mg, about 50-55 mg, about 55-60 mg,about 60-65 mg, about 65-70 mg, about 70-80 mg, about 80-90 mg, about80-120 mg, about 90-100 mg, about 100-120 mg, about 120-140 mg, about140-160 mg, about 160-180 mg, about 180-200 mg, about 10 mg, about 15mg, about 20 mg, about 30 mg, about 40 mg, about 60 mg, about 100 mg,about 150 mg, of the desvenlafaxine, or any dose in a range bounded byany of these values, may be administered.

For a combination of a duloxetine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 2-5 mg, about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9 mg,about 2-10 mg, about 2-11 mg, about 2-12 mg, about 2-13 mg, about 2-14mg, about 2-15 mg, about 2-20 mg, about 2-21 mg, about 2-22 mg, about2-23 mg, about 2-24 mg, about 2-25 mg, about 2-26 mg, about 2-27 mg,about 2-28 mg, about 2-29 mg, about 2-30 mg, about 2-35 mg, about 2-40mg, about 2-45 mg, about 2-60 mg, about 2-90 mg, about 2-120 mg, about5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about 20-40 mg,about 25-30 mg, about 30-35 mg, about 30-50 mg, about 35-40 mg, about40-45 mg, about 45-50 mg, about 50-55 mg, about 50-70 mg, about 55-60mg, about 60-65 mg, about 65-70 mg, about 70-80 mg, about 80-90 mg,about 90-100 mg, about 100-120 mg, about 120-140 mg, about 140-160 mg,about 160-180 mg, about 180-200 mg, about 10 mg, about 15 mg, about 20mg, about 30 mg, about 40 mg, about 60 mg, about 100 mg, about 120 mg,of the duloxetine, or any dose in a range bounded by any of thesevalues, may be administered.

For a combination of a mirtazapine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 2-5 mg,about 2-6 mg, about 2-7 mg, about 2-8 mg, about 2-9 mg, about 2-10 mg,about 2-11 mg, about 2-12 mg, about 2-13 mg, about 2-14 mg, about 2-15mg, about 2-20 mg, about 2-25 mg, about 2-30 mg, about 2-35 mg, about2-40 mg, about 2-45 mg, about 1-5 mg, about 5-10 mg, about 5-100 mg,about 10-15 mg, about 10-50 mg, about 15-20 mg, about 15-45 mg, about20-25 mg, about 25-30 mg, about 30-35 mg, about 35-40 mg, about 40-45mg, about 45-50 mg, about 50-55 mg, about 55-60 mg, about 60-65 mg,about 65-70 mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about100-120 mg, about 120-140 mg, about 140-160 mg, about 160-180 mg, about180-200 mg, about 10 mg, about 15 mg, about 20 mg, about 30 mg, about 40mg, about 45 mg, about 60 mg, about 75 mg, of the mirtazapine, or anydose in a range bounded by any of these values, may be administered.

For a combination of a nefazodone and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 10-20 mg, about 20-40 mg, about 20-50 mg, about 20-60 mg, about20-70 mg, about 20-80 mg, about 20-90 mg, about 20-100 mg, about 20-120mg, about 20-140 mg, about 20-160 mg, about 20-180 mg, about 20-200 mg,about 20-250 mg, about 20-300 mg, about 20-450 mg, about 20-600 mg,about 20-25 mg, about 25-30 mg, about 30-40 mg, about 40-50 mg, about50-60 mg, about 60-70 mg, about 70-80 mg, about 80-90 mg, about 80-120mg, about 90-100 mg, about 100-120 mg, about 120-140 mg, about 140-150mg, about 150-160 mg, about 160-180 mg, about 160-240 mg, about 180-200mg, about 200-220 mg, about 220-240 mg, about 240-250 mg, about 250-260mg, about 260-280 mg, about 280-300 mg, about 300-320 mg, about 320-350mg, about 350-400 mg, about 400-450 mg, about 450-500 mg, about 500-550mg, about 550-600 mg, about 600-650 mg, about 650-700 mg, about 700-1000mg, about 1000-1500 mg, about 25 mg, about 50 mg, about 75 mg, about 100mg, about 150 mg, about 250 mg, about 300 mg, about 400 mg, about 600mg, of the nefazodone, or any dose in a range bounded by any of thesevalues, may be administered.

For a combination of a selegiline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.5-2mg, about 2-5 mg, about 1-10 mg, about 1-9 mg, about 1-8 mg, about 1-7mg, about 1-6 mg, about 1-5 mg, about 1-3 mg, about 3-5 mg, about 5-10mg, about 5-15 mg, about 10-15 mg, about 15-25 mg, about 25-30 mg, about30-35 mg, about 35-40 mg, about 40-45 mg, about 45-50 mg, about 5 mg,about 10 mg, about 15 mg, about 20 mg, about 30 mg, about 40 mg, of theselegiline, or any dose in a range bounded by any of these values, maybe administered.

For a combination of a sibutramine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-5 mg,about 1-15 mg, about 1-10 mg, about 1-8 mg, about 5-10 mg, about 10-15mg, about 15-20 mg, about 20-25 mg, about 25-30 mg, about 30-35 mg,about 35-40 mg, about 40-45 mg, about 45-50 mg, about 50-55 mg, about55-60 mg, about 60-65 mg, about 65-70 mg, about 70-80 mg, about 80-90mg, about 90-100 mg, about 100-120 mg, about 120-140 mg, about 5 mg,about 10 mg, about 15 mg, about 20 mg, about 30 mg, about 40 mg, about60 mg, about 100 mg, about 120 mg, of the sibutramine, or any dose in arange bounded by any of these values, may be administered.

For a combination of a rasagiline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.3mg, about 0.3-0.5 mg, about 0.3-0.7 mg, about 0.5-0.7 mg, about 0.5-1.5mg, about 0.7-0.9 mg, about 0.9-1.0 mg, about 1.0-1.5 mg, about 1.5-2.0mg, about 2.0-3.0 mg, about 0.1 mg, about 0.25 mg, about 0.5 mg, about0.75 mg, about 1 mg, about 2 mg, of the rasagiline, or any dose in arange bounded by any of these values, may be administered.

For a combination of a milnacipran and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-7.5mg, about 7.5-12.5 mg, about 5-20 mg, about 5-100 mg, about 5-90 mg,about 5-80 mg, about 5-70 mg, about 5-60 mg, about 5-50 mg, about 5-40mg, about 12.5-15 mg, about 15-20 mg, about 20-30 mg, about 20-25 mg,about 25-30 mg, about 30-35 mg, about 35-40 mg, about 40-45 mg, about45-50 mg, about 50-55 mg, about 40-60 mg, about 55-60 mg, about 60-65mg, about 65-70 mg, about 70-80 mg, about 80-90 mg, about 90-100 mg,about 80-120 mg, about 100-120 mg, about 120-140 mg, about 140-160 mg,about 160-180 mg, about 180-200 mg, about 180-220 mg, about 200-300 mg,about 300-400 mg, about 7.5 mg, about 12.5 mg, about 25 mg, about 50 mg,about 75 mg, about 60 mg, about 100 mg, about 200 mg, of themilnacipran, or any dose in a range bounded by any of these values, maybe administered.

For a combination of a moclobemide and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 1-10 mg,about 10-20 mg, about 20-25 mg, about 20-450 mg, about 20-300 mg, about20-250 mg, about 20-200 mg, about 20-150 mg, about 20-100 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-320 mg, about 280-300 mg,about 300-320 mg, about 320-350 mg, about 350-400 mg, about 430-470 mg,about 400-450 mg, about 450-500 mg, about 500-550 mg, about 550-600 mg,about 600-650 mg, about 650-700 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the moclobemide, or any dose in a range bounded byany of these values, may be administered.

For a combination of a nialamide and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the nialamide, or any dose in a range bounded byany of these values, may be administered.

For a combination of a iproniazid and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the iproniazid, or any dose in a range bounded byany of these values, may be administered.

For a combination of a iproclozide and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the iproclozide, or any dose in a range bounded byany of these values, may be administered.

For a combination of a toloxatone and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the toloxatone, or any dose in a range bounded byany of these values, may be administered.

For a combination of a butriptyline and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the butriptyline, or any dose in a range bounded byany of these values, may be administered.

For a combination of a dosulepin and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the dosulepin, or any dose in a range bounded byany of these values, may be administered.

For a combination of a dibenzepin and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the dibenzepin, or any dose in a range bounded byany of these values, may be administered.

For a combination of a iprindole and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the iprindole, or any dose in a range bounded byany of these values, may be administered.

For a combination of a lofepramine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the lofepramine, or any dose in a range bounded byany of these values, may be administered.

For a combination of a opipramol and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the opipramol, or any dose in a range bounded byany of these values, may be administered.

For a combination of a norfluoxetine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the norfluoxetine, or any dose in a range boundedby any of these values, may be administered.

For a combination of a dapoxetine and a dextromethorphan (includingdeuterium-modified dextromethorphan, e.g. d6-dextromethorphan, andnon-deuterium modified dextromethorphan), a daily dose of about 0.1-0.25mg, about 0.25-0.5 mg, about 0.5-0.75 mg, about 0.75-1 mg, about 1-5 mg,about 5-10 mg, about 10-15 mg, about 15-20 mg, about 20-25 mg, about25-30 mg, about 30-40 mg, about 40-50 mg, about 50-60 mg, about 60-70mg, about 70-80 mg, about 80-90 mg, about 90-100 mg, about 100-120 mg,about 120-140 mg, about 140-150 mg, about 150-160 mg, about 160-180 mg,about 180-200 mg, about 200-220 mg, about 220-240 mg, about 240-250 mg,about 250-260 mg, about 260-280 mg, about 280-300 mg, about 300-320 mg,about 320-350 mg, about 350-400 mg, about 400-450 mg, about 450-500 mg,about 500-550 mg, about 550-600 mg, about 600-650 mg, about 650-700 mg,about 700-800 mg, about 800-1000 mg, about 25 mg, about 50 mg, about 75mg, about 100 mg, about 150 mg, about 250 mg, about 300 mg, about 400mg, about 600 mg, of the dapoxetine, or any dose in a range bounded byany of these values, may be administered.

Bupropion has the structure shown below (bupropion hydrochloride formshown).

Combining bupropion with dextromethorphan may provide greater efficacy,such as greater pain relief, than would otherwise be achieved byadministering either component alone. In extensive metabolizers,dextromethorphan can be rapidly and extensively metabolized, yieldinglow systemic exposure even at high doses. Bupropion, besides possessinganti-depressant and analgesic properties, is an inhibitor ofdextromethorphan metabolism. Bupropion is a dopamine and norepinephrinereuptake inhibitor. It can also be a nicotinic acetylcholine receptorantagonist, and it can modulate cytokines associated with inflammatorydiseases. Bupropion can affect levels of tumor necrosis factor-alpha andinterferon-gamma. Metabolites of bupropion, which includehydroxybupropion, threohydroxybupropion (also known asthreohydrobupropion or threodihydrobupropion), anderythrohydroxybupropion (also known as erythrohydrobupropion orerythrodihydrobupropion), are also inhibitors of dextromethorphanmetabolism. Thus, bupropion, including a form of bupropion that israpidly converted in the body (such as a salt, hydrate, solvate,polymorph, etc.), is a prodrug of hydroxybupropion,threohydroxybupropion, and erythrohydroxybupropion. Prodrugs ofbupropion can include N-methylbupropion and N-benzylbupropion.

As explained above, this inhibition may augment dextromethorphan plasmalevels, resulting in additive or synergistic efficacy such as relief ofneurological disorders including pain, depression, smoking cessation,etc. Thus, while inhibition of dextromethorphan metabolism is only oneof many potential benefits of the combination, co-administration ofdextromethorphan with bupropion may thereby enhance the efficacy ofbupropion for many individuals. Co-administration of dextromethorphanwith bupropion may enhance the analgesic properties of bupropion formany individuals. Co-administration of dextromethorphan with bupropionmay also enhance the antidepressant properties of bupropion for manyindividuals, including faster onset of action.

Another potential benefit of co-administration of dextromethorphan andbupropion is that it may be useful to reduce the potential for anadverse event, such as somnolence, associated with treatment bydextromethorphan. This may be useful, for example, in human patients atrisk of experiencing the adverse event as a result of being treated withdextromethorphan.

Another potential benefit of co-administration of dextromethorphan andbupropion is that it may be useful to reduce the potential for anadverse event, such as seizure, associated with treatment by bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds. This may be useful, forexample, in human patients at risk of experiencing the adverse event asa result of being treated with bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds.

With respect to dextromethorphan, bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, co-administration may reduce acentral nervous system adverse event, a gastrointestinal event, oranother type of adverse event associated with any of these compounds.Central nervous system (CNS) adverse events include, but are not limitedto, nervousness, dizziness, sleeplessness, light-headedness, tremor,hallucinations, convulsions, CNS depression, fear, anxiety, headache,increased irritability or excitement, tinnitus, drowsiness, dizziness,sedation, somnolence, confusion, disorientation, lassitude,incoordination, fatigue, euphoria, nervousness, insomnia, sleepingdisturbances, convulsive seizures, excitation, catatonic-like states,hysteria, hallucinations, delusions, paranoia, headaches and/ormigraine, and extrapyramidal symptoms such as oculogyric crisis,torticollis, hyperexcitability, increased muscle tone, ataxia, and/ortongue protrusion.

Gastrointestinal adverse events include, but are not limited to, nausea,vomiting, abdominal pain, dysphagia, dyspepsia, diarrhea, abdominaldistension, flatulence, peptic ulcers with bleeding, loose stools,constipation, stomach pain, heartburn, gas, loss of appetite, feeling offullness in stomach, indigestion, bloating, hyperacidity, dry mouth,gastrointestinal disturbances, and gastric pain.

Co-administering dextromethorphan and an antidepressant, such asbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, does not necessarily require that the two compounds beadministered in the same dosage form. For example, the two compounds maybe administered in a single dosage form, or they may be administered intwo separate dosage forms. Additionally, the two compounds may beadministered at the same time, but this is not required. The compoundscan be given at different times as long as both are in a human body atthe same time for at least a portion of the time that treatment byco-administration is being carried out.

Side effects of bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, and/or dextromethorphan may be reduced byadministering bupropion, hydroxybupropion, erythrohydroxybupropion, orthreohydroxybupropion, with dextromethorphan. Examples of side effectsthat may be reduced include abnormal sensation of rotation and movement,agitation, arm weakness, bloating, blurred vision, burning sensation inthe eyes, buzzing sound(s) in the ear(s), changes in vital signs(including, but not limited to, heart rate, respiratory rate, bodytemperature, and blood pressure), cold sensation, constipation,difficulty concentrating, difficulty sleeping, difficulty in fallingasleep, difficulty urinating, difficulty with bowel movement, discomfortin the ear, discomfort in the eye, discomfort in the stomach, dizziness,dry lips, dry mouth, dry throat, dysmenorrhea, fatigue, feelingfeverish, feeling heavy headed, feeling more agitated than usual,feeling more tired than usual, feeling tired, hand tremors, handweakness, headache, heartburn, hot flashes, increased blood pressure,increased skin sensitivity, increased skin sensitivity at head and face,involuntary muscle contraction, involuntary muscle contractions all overthe body, knee pain, leg weakness, lightheadedness, loose stool, loss ofappetite, low back pain, menstrual disorder, metallic taste, more salivathan usual, mucosal dryness, nasal congestion, nausea, runny nose,sensation of light pressure sensation in the eyes, shivers whenstretching or yawning, skin sensitivity, skin sensitivity in arm, face,and/or head, sleep difficulties, soft stools, stomach ache, stomachdiscomfort, sweaty hands and/or feet, throat irritation, throat pain,tinnitus, tremors, and/or weakness. Any of these side effects may alsobe referred to, or grouped, according to a corresponding, equivalent, orotherwise relevant term found in the Medical Dictionary for RegulatoryActivities (MedRA).

In some embodiments, co-administration of a combination of bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, and dextromethorphanresults in both bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan contributing to the pain relievingproperties of the combination. For example, the combination may haveimproved pain relieving properties as compared to bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, alone or compared todextromethorphan alone, including potentially faster onset of action.

In some embodiments, the combination may have improved pain relievingproperties of at least about 0.5%, at least about 1%, at least about10%, at least about 20%, at least about 30%, at least about 50%, atleast 100%, up to about 500% or up to 1000%, about 0.5% to about 1000%,about 10% to about 20%, about 20% to about 30%, about 30% to about 40%,about 40% to about 50%, about 50% to about 60%, about 60% to about 70%,about 70% to about 80%, about 80% to about 90%, about 90% to about 100%,about 100% to about 110%, about 110% to about 120%, about 120% to about130%, about 130% to about 140%, about 140% to about 150%, about 150% toabout 160%, about 160% to about 170%, about 170% to about 180%, about180% to about 190%, about 190% to about 200%, or any amount of painrelief in a range bounded by, or between, any of these values, ascompared to bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, alone.

In some embodiments, the combination may have improved pain relievingproperties of at least about 0.5%, at least about 1%, at least about10%, at least about 20%, at least about 30%, at least about 50%, atleast 100%, up to about 500% or up to 1000%, about 0.5% to about 1000%,about 10% to about 20%, about 20% to about 30%, about 30% to about 40%,about 40% to about 50%, about 50% to about 60%, about 60% to about 70%,about 70% to about 80%, about 80% to about 90%, about 90% to about 100%,about 100% to about 110%, about 110% to about 120%, about 120% to about130%, about 130% to about 140%, about 140% to about 150%, about 150% toabout 160%, about 160% to about 170%, about 170% to about 180%, about180% to about 190%, about 190% to about 200%, or any amount of painrelief in a range bounded by, or between, any of these values, ascompared to as compared to dextromethorphan alone.

Unless otherwise indicated, any reference to a compound herein, such asdextromethorphan, bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, by structure, name, or any other means, includespharmaceutically acceptable salts; alternate solid forms, such aspolymorphs, solvates, hydrates, etc.; tautomers; deuterium-modifiedcompounds, such as deuterium modified dextromethorphan; or any chemicalspecies that may rapidly convert to a compound described herein underconditions in which the compounds are used as described herein.

In some embodiments, an excess of one stereoisomer of bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds may be administered. Inother embodiments, an excess of the S-enantiomer (such as at least 60%,at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, atleast 95%, at least 99% or enantiomerically pure S-enantiomer) or anexcess of the R-enantiomer (such as at least 60%, at least 70%, at least75%, at least 80%, at least 85%, at least 90%, at least 95%, at least99% or enantiomerically pure R-enantiomer) of bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds may be administered.

Examples of deuterium-enriched bupropion, and/or enantiopuredeuterium-enriched bupropion include, but are not limited to, thoseshown below.

In some embodiments, both dextromethorphan and bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, ametabolite, or prodrug of any of these compounds are formulated to beimmediate release, and in other embodiments both bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, ametabolite or prodrug of any of these compounds are formulated to besustained release.

Examples of deuterium modified dextromethorphan include, but are notlimited to, those shown below.

d6-dextromethorphan

A dosage form or a composition may be a blend or mixture ofdextromethorphan and a compound that inhibits the metabolism ofdextromethorphan, such as bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, either alone or within a vehicle. Forexample, dextromethorphan and bupropion may be dispersed within eachother or dispersed together within a vehicle. A dispersion may include amixture of solid materials wherein small individual particles aresubstantially one compound, but the small particles are dispersed withinone another, such as might occur if two powders of two different drugsare blended with a solid vehicle material, and the blending is done inthe solid form. In some embodiments, dextromethorphan and bupropion maybe substantially uniformly dispersed within a composition or dosageform. Alternatively, dextromethorphan and bupropion may be in separatedomains or phases within a composition or dosage form. For example, onedrug may be in a coating and another drug may be in a core within thecoating. For example, one drug may be formulated for sustained releaseand another drug may be formulated for immediate release.

Some embodiments include administration of a tablet that containsbupropion in a form that provides sustained release and dextromethorphanin a form that provides immediate release. While there are many waysthat sustained release of bupropion may be achieved, in someembodiments, bupropion is combined with hydroxypropyl methylcellulose.For example, particles of bupropion hydrochloride could be blended withmicrocrystalline cellulose and hydroxypropyl methylcellulose (e.g.,METHOCEL®) to form an admixture of blended powders. This could then becombined with immediate release dextromethorphan in a single tablet.

Dextromethorphan and/or an antidepressant, such as bupropion,hydroxybupropion, threohydroxybupropion and erythrohydroxybupropion, ora non-bupropion antidepressant (all of which are referred tocollectively herein as “therapeutic compounds” for convenience) may becombined with a pharmaceutical carrier selected on the basis of thechosen route of administration and standard pharmaceutical practice asdescribed, for example, in Remington's Pharmaceutical Sciences, 2005.The relative proportions of active ingredient and carrier may bedetermined, for example, by the solubility and chemical nature of thecompounds, chosen route of administration and standard pharmaceuticalpractice.

Therapeutic compounds may be administered by any means that may resultin the contact of the active agent(s) with the desired site or site(s)of action in the body of a patient. The compounds may be administered byany conventional means available for use in conjunction withpharmaceuticals, either as individual therapeutic agents or in acombination of therapeutic agents. For example, they may be administeredas the sole active agents in a pharmaceutical composition, or they canbe used in combination with other therapeutically active ingredients.

Therapeutic compounds may be administered to a human patient in avariety of forms adapted to the chosen route of administration, e.g.,orally or parenterally. Parenteral administration in this respectincludes administration by the following routes: intravenous,intramuscular, subcutaneous, intraocular, intrasynovial, transepithelialincluding transdermal, ophthalmic, sublingual and buccal; topicallyincluding ophthalmic, dermal, ocular, rectal and nasal inhalation viainsufflation, aerosol and rectal systemic.

The ratio of dextromethorphan to bupropion may vary. In someembodiments, the weight ratio of dextromethorphan to bupropion may beabout 0.1 to about 10, about 0.1 to about 2, about 0.2 to about 1, about0.1 to about 0.5, about 0.1 to about 0.3, about 0.2 to about 0.4, about0.3 to about 0.5, about 0.5 to about 0.7, about 0.8 to about 1, about0.2, about 0.3, about 0.4, about 0.45, about 0.6, about 0.9, or anyratio in a range bounded by, or between, any of these values. A ratio of0.1 indicates that the weight of dextromethorphan is 1/10 that ofbupropion. A ratio of 10 indicates that the weight of dextromethorphanis 10 times that of bupropion.

The amount of dextromethorphan in a therapeutic composition may vary.For example, some liquid compositions may comprise about 0.0001% (w/v)to about 50% (w/v), about 0.01% (w/v) to about 20% (w/v), about 0.01% toabout 10% (w/v), about 0.001% (w/v) to about 1% (w/v), about 0.1% (w/v)to about 0.5% (w/v), about 1% (w/v) to about 3% (w/v), about 3% (w/v) toabout 5% (w/v), about 5% (w/v) to about 7% (w/v), about 7% (w/v) toabout 10% (w/v), about 10% (w/v) to about 15% (w/v), about 15% (w/v) toabout 20% (w/v), about 20% (w/v) to about 30% (w/v), about 30% (w/v) toabout 40% (w/v), or about 40% (w/v) to about 50% (w/v) ofdextromethorphan.

Some liquid dosage forms may contain about 10 mg to about 500 mg, about30 mg to about 350 mg, about 50 mg to about 200 mg, about 50 mg to about70 mg, about 20 mg to about 50 mg, about 30 mg to about 60 mg, about 40mg to about 50 mg, about 40 mg to about 55 mg, about 40 mg to about 42mg, about 42 mg to about 44 mg, about 44 mg to about 46 mg, about 46 mgto about 48 mg, about 48 mg to about 50 mg, about 80 mg to about 100 mg,about 110 mg to about 130 mg, about 170 mg to about 190 mg, about 45 mg,about 60 mg, about 90 mg, about 120 mg, or about 180 mg ofdextromethorphan, or any amount of dextromethorphan in a range boundedby, or between, any of these values.

Some solid compositions may comprise at least about 5% (w/w), at leastabout 10% (w/w), at least about 20% (w/w), at least about 50% (w/w), atleast about 70% (w/w), at least about 80%, about 10% (w/w) to about 30%(w/w), about 10% (w/w) to about 20% (w/w), about 20% (w/w) to about 30%(w/w), about 30% (w/w) to about 50% (w/w), about 30% (w/w) to about 40%(w/w), about 40% (w/w) to about 50% (w/w), about 50% (w/w) to about 80%(w/w), about 50% (w/w) to about 60% (w/w), about 70% (w/w) to about 80%(w/w), or about 80% (w/w) to about 90% (w/w) of dextromethorphan.

Some solid dosage forms may contain about 10 mg to about 500 mg, about30 mg to about 350 mg, about 20 mg to about 50 mg, about 30 mg to about60 mg, about 40 mg to about 50 mg, about 40 mg to about 42 mg, about 42mg to about 44 mg, about 44 mg to about 46 mg, about 46 mg to about 48mg, about 48 mg to about 50 mg, about 50 mg to about 200 mg, about 50 mgto about 70 mg, about 80 mg to about 100 mg, about 110 mg to about 130mg, about 170 mg to about 190 mg, about 60 mg, about 90 mg, about 120mg, or about 180 mg of dextromethorphan, or any amount ofdextromethorphan in a range bounded by, or between, any of these values.

In some embodiments, the amount of dextromethorphan may range from about0.1 mg/kg to about 20 mg/kg, about 0.75 mg/kg to about 7.5 mg/kg, about0.1 mg/kg to about 5 mg/kg, about 0.1 mg/kg to about 3 mg/kg, about 0.3mg/kg to about 0.9 mg/kg, about 0.3 mg/kg to about 1 mg/kg, about 0.6mg/kg to about 0.8 mg/kg, about 0.7 mg/kg to about 0.8 mg/kg, about 0.75mg/kg, about 0.4 mg/kg to about 1.5 mg/kg, about 1 mg/kg to about 2mg/kg, about 10 mg/kg to about 20 mg/kg, about 12 mg/kg to about 17mg/kg, about 15 mg/kg to about 20 mg/kg, about 1 mg/kg, about 1 mg/kg toabout 10 mg/kg, or any value bounded by or in between these ranges basedon the body weight of the patient.

The amount of bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, in a therapeutic composition may vary. If increasing theplasma level of dextromethorphan is desired, bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds, should be administeredin an amount that increases the plasma level of dextromethorphan. Forexample, bupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, may be administered in an amount that results in a plasmaconcentration of dextromethorphan in the human being, on day 8, day 9,or day 10, that is at least about 2 times, at least about 5 times, atleast about 10 times, at least about 15 times, at least about 20 times,at least about 30 times, at least about 40 times, at least about 50times, at least about 60 times, at least about 70 times, or at leastabout 80 times, the plasma concentration of the same amount ofdextromethorphan administered without bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, may be administered to a human beingin an amount that results in a 12 hour area under the curve from thetime of dosing (AUC₀₋₁₂), or average plasma concentration in the humanbeing for the 12 hours following dosing (C_(avg)) of dextromethorphan,on day 8, day 9, or day 10, that is at least about 2 times, at leastabout 5 times, at least about 10 times, at least about 15 times, atleast about 20 times, at least about 30 times, at least about 40 times,at least about 50 times, at least about 60 times, at least about 70times, or at least about 80 times the plasma concentration of the sameamount of dextromethorphan administered without bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds.

In some embodiments, bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a metabolite orprodrug of any of these compounds, may be administered to a human beingin an amount that results in a maximum plasma concentration (C_(max)) ofdextromethorphan in the human being, on day 8, day 9, or day 10, that isat least about 2 times, at least about 5 times, at least about 10 times,at least about 15 times, at least about 20 times, at least about 30times, or at least about 40 times the plasma concentration of the sameamount of dextromethorphan administered without bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or ametabolite or prodrug of any of these compounds.

For co-administration of bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, an increase in the dextromethorphanplasma level can occur on the first day that bupropion,hydroxybupropion, threohydroxybupropion, erythrohydroxybupropion, or ametabolite or prodrug of any of these compounds, is administered, ascompared to the same amount of dextromethorphan administered withoutbupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds. For example, the dextromethorphan plasma level on the firstday that bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, is administered may be at least about 1.5 times, at leastabout at least 2 times, at least about 2.5 times, at least about 3times, at least about 4 times, at least about 5 times, at least about 6times at least about 7 times, at least about 8 times, at least about 9times, or at least about 10 times the level that would be achieved byadministering the same amount of dextromethorphan without bupropion,hydroxybupropion, threohydroxybupropion, erythrohydroxybupropion, or ametabolite or prodrug of any of these compounds.

In some embodiments, the dextromethorphan AUC on the first day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least twicethe AUC that would be achieved by administering the same amount ofdextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextromethorphan AUC₀₋₁₂ on the first day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about15 ng·hr/mL, at least about 17 ng·hr/mL, at least about 19 ng·hr/mL, atleast about 20 ng·hr/mL, at least about 22 ng·hr/mL, at least about 23ng·hr/mL, at least about 24 ng·hr/mL, at least about 25 ng·hr/mL, atleast about 26 ng·hr/mL, at least about 27 ng·hr/mL, at least about 28ng·hr/mL, at least about 29 ng·hr/mL, at least about 30 ng·hr/mL, atleast about 31 ng·hr/mL, at least about 32 ng·hr/mL, at least about 33ng·hr/mL, at least about 34 ng·hr/mL, at least about 35 ng·hr/mL, atleast about 36 ng·hr/mL, at least about 37 ng·hr/mL, at least about 38ng·hr/mL, at least about 39 ng·hr/mL, at least about 40 ng·hr/mL, atleast about 41 ng·hr/mL, at least about 42 ng·hr/mL, at least about 43ng·hr/mL, at least about 44 ng·hr/mL, at least about 45 ng·hr/mL, atleast about 46 ng·hr/mL, at least about 47 ng·hr/mL, at least about 48ng·hr/mL, at least about 49 ng·hr/mL, at least about 50 ng·hr/mL, atleast about 51 ng·hr/mL, at least about 52 ng·hr/mL, at least about 53ng·hr/mL, at least about 54 ng·hr/mL, at least about 55 ng·hr/mL, atleast about 56 ng·hr/mL, at least about or 56.7 ng·hr/mL, and may be upto 10,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC₀₋₁₂ on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about40 ng·hr/mL, at least about 50 ng·hr/mL, at least about 60 ng·hr/mL, atleast about 70 ng·hr/mL, at least about 80 ng·hr/mL, at least about 90ng·hr/mL, at least about 100 ng·hr/mL, at least about 150 ng·hr/mL, atleast about 200 ng·hr/mL, at least about 250 ng·hr/mL, at least about300 ng·hr/mL, at least about 350 ng·hr/mL, at least about 400 ng·hr/mL,at least about 450 ng·hr/mL, at least about 500 ng·hr/mL, at least about550 ng·hr/mL, about 500 ng·hr/mL to about 600 ng·hr/mL, about 500ng·hr/mL to about 550 ng·hr/mL, about 500 ng·hr/mL to about 525ng·hr/mL, about 525 ng·hr/mL to about 600 ng·hr/mL, at least about 600ng·hr/mL, at least about 650 ng·hr/mL, at least about 700 ng·hr/mL, atleast about 750 ng·hr/mL, at least about 800 ng·hr/mL, about 800ng·hr/mL to about 900 ng·hr/mL, about 850 ng·hr/mL to about 900ng·hr/mL, about 850 ng·hr/mL to about 875 ng·hr/mL, about 875 ng·hr/mLto about 900 ng·hr/mL, about 900 ng·hr/mL to about 1,000 ng·hr/mL, about1,000 ng·hr/mL to about 1,100 ng·hr/mL, about 1,100 ng·hr/mL to about1,200 ng·hr/mL, about 1,200 ng·hr/mL to about 1,300 ng·hr/mL, about1,300 ng·hr/mL to about 1,400 ng·hr/mL, about 1,400 ng·hr/mL to about1,500 ng·hr/mL, about 1,500 ng·hr/mL to about 1,600 ng·hr/mL, about1,600 ng·hr/mL to about 1,700 ng·hr/mL, about 1,700 ng·hr/mL to about1,800 ng·hr/mL, about 1,800 ng·hr/mL to about 2,000 ng·hr/mL, at leastabout 850 ng·hr/mL, at least about 900 ng·hr/mL, at least about 950ng·hr/mL, at least about 1000 ng·hr/mL, at least about 1050 ng·hr/mL, atleast about 1100 ng·hr/mL, at least about 1150 ng·hr/mL, at least about1200 ng·hr/mL, at least about 1250 ng·hr/mL, at least about 1300ng·hr/mL, at least about 1350 ng·hr/mL, at least about 1400 ng·hr/mL, atleast about 1450 ng·hr/mL, at least about 1500 ng·hr/mL, at least about1550 ng·hr/mL, at least about 1600 ng·hr/mL, at least about 1625ng·hr/mL, at least about 1650 ng·hr/mL, at least about 1675 ng·hr/mL, orat least about 1686.3 ng·hr/mL, and, in some embodiments, may be up toabout 50,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC₀₋₂₄ on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about50 ng·hr/mL, at least about 75 ng·hr/mL, at least about 100 ng·hr/mL, atleast about 200 ng·hr/mL, at least about 300 ng·hr/mL, at least about400 ng·hr/mL, at least about 500 ng·hr/mL, at least about 600 ng·hr/mL,at least about 700 ng·hr/mL, at least about 800 ng·hr/mL, at least about900 ng·hr/mL, at least about 1000 ng·hr/mL, at least about 1100ng·hr/mL, at least about 1200 ng·hr/mL, at least about 1300 ng·hr/mL, atleast about 1400 ng·hr/mL, at least about 1500 ng·hr/mL, at least about1600 ng·hr/mL, at least about 1700 ng·hr/mL, at least about 1800ng·hr/mL, at least about 1900 ng·hr/mL, at least about 2000 ng·hr/mL, atleast about 2100 ng·hr/mL, at least about 2200 ng·hr/mL, at least about2300 ng·hr/mL, at least about 2400 ng·hr/mL, at least about 2500ng·hr/mL, at least about 2600 ng·hr/mL, at least about 2700 ng·hr/mL, atleast about 2800 ng·hr/mL, at least about 1850 ng·hr/mL, at least about2900 ng·hr/mL, at least about 2950 ng·hr/mL, or at least about 2975.3ng·hr/mL, and, in some embodiments, may be up to about 100,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC_(0-inf) on the eighth daythat the dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about75 ng·hr/mL, at least about 100 ng·hr/mL, at least about 200 ng·hr/mL,at least about 300 ng·hr/mL, at least about 400 ng·hr/mL, at least about500 ng·hr/mL, at least about 600 ng·hr/mL, at least about 700 ng·hr/mL,at least about 800 ng·hr/mL, at least about 900 ng·hr/mL, at least about1000 ng·hr/mL, at least about 1100 ng·hr/mL, at least about 1200ng·hr/mL, at least about 1300 ng·hr/mL, at least about 1400 ng·hr/mL, atleast about 1500 ng·hr/mL, at least about 1600 ng·hr/mL, at least about1700 ng·hr/mL, at least about 1800 ng·hr/mL, at least about 1900ng·hr/mL, at least about 2000 ng·hr/mL, at least about 2100 ng·hr/mL, atleast about 2200 ng·hr/mL, at least about 2300 ng·hr/mL, at least about2400 ng·hr/mL, at least about 2500 ng·hr/mL, at least about 2600ng·hr/mL, at least about 2700 ng·hr/mL, at least about 2800 ng·hr/mL, atleast about 2900 ng·hr/mL, at least about 3000 ng·hr/mL, at least about3100 ng·hr/mL, at least about 3200 ng·hr/mL, at least about 3300ng·hr/mL, at least about 3400 ng·hr/mL, at least about 3500 ng·hr/mL, atleast about 3600 ng·hr/mL, at least about 3700 ng·hr/mL, at least about3800 ng·hr/mL, at least about 3900 ng·hr/mL, at least about 4000ng·hr/mL, at least about 4100 ng·hr/mL, at least about 4200 ng·hr/mL, atleast about 4300 ng·hr/mL, at least about 4400 ng·hr/mL, at least about4500 ng·hr/mL, at least about 4600 ng·hr/mL, at least about 4700ng·hr/mL, at least about 4800 ng·hr/mL, at least about 4900 ng·hr/mL, atleast about 5000 ng·hr/mL, at least about 5100 ng·hr/mL, at least about5200 ng·hr/mL, at least about 5300 ng·hr/mL, at least about 5400ng·hr/mL, at least about 5500 ng·hr/mL, at least about 5600 ng·hr/mL, atleast about 5700 ng·hr/mL, at least about 5800 ng·hr/mL, at least about5900 ng·hr/mL, at least about 6000 ng·hr/mL, at least about 6100ng·hr/mL, at least about 6200 ng·hr/mL, at least about 6300 ng·hr/mL, atleast about 6400 ng·hr/mL, at least about 6500 ng·hr/mL, at least about6600 ng·hr/mL, at least about 6700 ng·hr/mL, at least about 6800ng·hr/mL, at least about 6900 ng·hr/mL, at least about 7000 ng·hr/mL, atleast about 7100 ng·hr/mL, at least about 7150 ng·hr/mL, at least about7200 ng·hr/mL, or at least about 7237.3 ng·hr/mL, and, in someembodiments, may be up to about 100,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC₀₋₁₂ on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about40 ng·hr/mL, at least about 50 ng·hr/mL, at least about 60 ng·hr/mL, atleast about 70 ng·hr/mL, at least about 80 ng·hr/mL, at least about 90ng·hr/mL, at least about 100 ng·hr/mL, at least about 150 ng·hr/mL, atleast about 200 ng·hr/mL, at least about 250 ng·hr/mL, at least about300 ng·hr/mL, at least about 350 ng·hr/mL, at least about 400 ng·hr/mL,at least about 450 ng·hr/mL, at least about 500 ng·hr/mL, at least about550 ng·hr/mL, about 500 ng·hr/mL to about 600 ng·hr/mL, about 500ng·hr/mL to about 550 ng·hr/mL, about 500 ng·hr/mL to about 525ng·hr/mL, about 525 ng·hr/mL to about 600 ng·hr/mL, at least about 600ng·hr/mL, at least about 650 ng·hr/mL, at least about 700 ng·hr/mL, atleast about 750 ng·hr/mL, at least about 800 ng·hr/mL, about 800ng·hr/mL to about 900 ng·hr/mL, about 850 ng·hr/mL to about 900ng·hr/mL, about 850 ng·hr/mL to about 875 ng·hr/mL, about 875 ng·hr/mLto about 900 ng·hr/mL, about 900 ng·hr/mL to about 1,000 ng·hr/mL, about1,000 ng·hr/mL to about 1,100 ng·hr/mL, about 1,100 ng·hr/mL to about1,200 ng·hr/mL, about 1,200 ng·hr/mL to about 1,300 ng·hr/mL, about1,300 ng·hr/mL to about 1,400 ng·hr/mL, about 1,400 ng·hr/mL to about1,500 ng·hr/mL, about 1,500 ng·hr/mL to about 1,600 ng·hr/mL, about1,600 ng·hr/mL to about 1,700 ng·hr/mL, about 1,700 ng·hr/mL to about1,800 ng·hr/mL, about 1,800 ng·hr/mL to about 2,000 ng·hr/mL, at leastabout 850 ng·hr/mL, at least about 900 ng·hr/mL, at least about 950ng·hr/mL, at least about 1000 ng·hr/mL, at least about 1050 ng·hr/mL, atleast about 1100 ng·hr/mL, at least about 1150 ng·hr/mL, at least about1200 ng·hr/mL, at least about 1250 ng·hr/mL, at least about 1300ng·hr/mL, at least about 1350 ng·hr/mL, at least about 1400 ng·hr/mL, atleast about 1450 ng·hr/mL, at least about 1500 ng·hr/mL, at least about1550 ng·hr/mL, at least about 1600 ng·hr/mL, at least about 1625ng·hr/mL, at least about 1650 ng·hr/mL, at least about 1675 ng·hr/mL, orat least about 1686.3 ng·hr/mL, and, in some embodiments, may be up toabout 50,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC₀₋₂₄ on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about50 ng·hr/mL, at least about 75 ng·hr/mL, at least about 100 ng·hr/mL, atleast about 200 ng·hr/mL, at least about 300 ng·hr/mL, at least about400 ng·hr/mL, at least about 500 ng·hr/mL, at least about 600 ng·hr/mL,at least about 700 ng·hr/mL, at least about 800 ng·hr/mL, at least about900 ng·hr/mL, at least about 1000 ng·hr/mL, at least about 1100ng·hr/mL, at least about 1200 ng·hr/mL, at least about 1300 ng·hr/mL, atleast about 1400 ng·hr/mL, at least about 1500 ng·hr/mL, at least about1600 ng·hr/mL, at least about 1700 ng·hr/mL, at least about 1800ng·hr/mL, at least about 1900 ng·hr/mL, at least about 2000 ng·hr/mL, atleast about 2100 ng·hr/mL, at least about 2200 ng·hr/mL, at least about2300 ng·hr/mL, at least about 2400 ng·hr/mL, at least about 2500ng·hr/mL, at least about 2600 ng·hr/mL, at least about 2700 ng·hr/mL, atleast about 2800 ng·hr/mL, at least about 1850 ng·hr/mL, at least about2900 ng·hr/mL, at least about 2950 ng·hr/mL, or at least about 2975.3ng·hr/mL, and, in some embodiments, may be up to about 100,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC_(0-inf) on the ninth daythat the dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about75 ng·hr/mL, at least about 100 ng·hr/mL, at least about 200 ng·hr/mL,at least about 300 ng·hr/mL, at least about 400 ng·hr/mL, at least about500 ng·hr/mL, at least about 600 ng·hr/mL, at least about 700 ng·hr/mL,at least about 800 ng·hr/mL, at least about 900 ng·hr/mL, at least about1000 ng·hr/mL, at least about 1100 ng·hr/mL, at least about 1200ng·hr/mL, at least about 1300 ng·hr/mL, at least about 1400 ng·hr/mL, atleast about 1500 ng·hr/mL, at least about 1600 ng·hr/mL, at least about1700 ng·hr/mL, at least about 1800 ng·hr/mL, at least about 1900ng·hr/mL, at least about 2000 ng·hr/mL, at least about 2100 ng·hr/mL, atleast about 2200 ng·hr/mL, at least about 2300 ng·hr/mL, at least about2400 ng·hr/mL, at least about 2500 ng·hr/mL, at least about 2600ng·hr/mL, at least about 2700 ng·hr/mL, at least about 2800 ng·hr/mL, atleast about 2900 ng·hr/mL, at least about 3000 ng·hr/mL, at least about3100 ng·hr/mL, at least about 3200 ng·hr/mL, at least about 3300ng·hr/mL, at least about 3400 ng·hr/mL, at least about 3500 ng·hr/mL, atleast about 3600 ng·hr/mL, at least about 3700 ng·hr/mL, at least about3800 ng·hr/mL, at least about 3900 ng·hr/mL, at least about 4000ng·hr/mL, at least about 4100 ng·hr/mL, at least about 4200 ng·hr/mL, atleast about 4300 ng·hr/mL, at least about 4400 ng·hr/mL, at least about4500 ng·hr/mL, at least about 4600 ng·hr/mL, at least about 4700ng·hr/mL, at least about 4800 ng·hr/mL, at least about 4900 ng·hr/mL, atleast about 5000 ng·hr/mL, at least about 5100 ng·hr/mL, at least about5200 ng·hr/mL, at least about 5300 ng·hr/mL, at least about 5400ng·hr/mL, at least about 5500 ng·hr/mL, at least about 5600 ng·hr/mL, atleast about 5700 ng·hr/mL, at least about 5800 ng·hr/mL, at least about5900 ng·hr/mL, at least about 6000 ng·hr/mL, at least about 6100ng·hr/mL, at least about 6200 ng·hr/mL, at least about 6300 ng·hr/mL, atleast about 6400 ng·hr/mL, at least about 6500 ng·hr/mL, at least about6600 ng·hr/mL, at least about 6700 ng·hr/mL, at least about 6800ng·hr/mL, at least about 6900 ng·hr/mL, at least about 7000 ng·hr/mL, atleast about 7100 ng·hr/mL, at least about 7150 ng·hr/mL, at least about7200 ng·hr/mL, or at least about 7237.3 ng·hr/mL, and, in someembodiments, may be up to about 100,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC₀₋₁₂ on the tenth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about40 ng·hr/mL, at least about 50 ng·hr/mL, at least about 60 ng·hr/mL, atleast about 70 ng·hr/mL, at least about 80 ng·hr/mL, at least about 90ng·hr/mL, at least about 100 ng·hr/mL, at least about 150 ng·hr/mL, atleast about 200 ng·hr/mL, at least about 250 ng·hr/mL, at least about300 ng·hr/mL, at least about 350 ng·hr/mL, at least about 400 ng·hr/mL,at least about 450 ng·hr/mL, at least about 500 ng·hr/mL, at least about550 ng·hr/mL, about 500 ng·hr/mL to about 600 ng·hr/mL, about 500ng·hr/mL to about 550 ng·hr/mL, about 500 ng·hr/mL to about 525ng·hr/mL, about 525 ng·hr/mL to about 600 ng·hr/mL, at least about 600ng·hr/mL, at least about 650 ng·hr/mL, at least about 700 ng·hr/mL, atleast about 750 ng·hr/mL, at least about 800 ng·hr/mL, about 800ng·hr/mL to about 900 ng·hr/mL, about 850 ng·hr/mL to about 900ng·hr/mL, about 850 ng·hr/mL to about 875 ng·hr/mL, about 875 ng·hr/mLto about 900 ng·hr/mL, about 900 ng·hr/mL to about 1,000 ng·hr/mL, about1,000 ng·hr/mL to about 1,100 ng·hr/mL, about 1,100 ng·hr/mL to about1,200 ng·hr/mL, about 1,200 ng·hr/mL to about 1,300 ng·hr/mL, about1,300 ng·hr/mL to about 1,400 ng·hr/mL, about 1,400 ng·hr/mL to about1,500 ng·hr/mL, about 1,500 ng·hr/mL to about 1,600 ng·hr/mL, about1,600 ng·hr/mL to about 1,700 ng·hr/mL, about 1,700 ng·hr/mL to about1,800 ng·hr/mL, about 1,800 ng·hr/mL to about 2,000 ng·hr/mL, at leastabout 850 ng·hr/mL, at least about 900 ng·hr/mL, at least about 950ng·hr/mL, at least about 1000 ng·hr/mL, at least about 1050 ng·hr/mL, atleast about 1100 ng·hr/mL, at least about 1150 ng·hr/mL, at least about1200 ng·hr/mL, at least about 1250 ng·hr/mL, at least about 1300ng·hr/mL, at least about 1350 ng·hr/mL, at least about 1400 ng·hr/mL, atleast about 1450 ng·hr/mL, at least about 1500 ng·hr/mL, at least about1550 ng·hr/mL, at least about 1600 ng·hr/mL, at least about 1625ng·hr/mL, at least about 1650 ng·hr/mL, at least about 1675 ng·hr/mL, orat least about 1686.3 ng·hr/mL, and, in some embodiments, may be up toabout 50,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC₀₋₂₄ on the tenth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about50 ng·hr/mL, at least about 75 ng·hr/mL, at least about 100 ng·hr/mL, atleast about 200 ng·hr/mL, at least about 300 ng·hr/mL, at least about400 ng·hr/mL, at least about 500 ng·hr/mL, at least about 600 ng·hr/mL,at least about 700 ng·hr/mL, at least about 800 ng·hr/mL, at least about900 ng·hr/mL, at least about 1000 ng·hr/mL, at least about 1100ng·hr/mL, at least about 1200 ng·hr/mL, at least about 1300 ng·hr/mL, atleast about 1400 ng·hr/mL, at least about 1500 ng·hr/mL, at least about1600 ng·hr/mL, at least about 1700 ng·hr/mL, at least about 1800ng·hr/mL, at least about 1900 ng·hr/mL, at least about 2000 ng·hr/mL, atleast about 2100 ng·hr/mL, at least about 2200 ng·hr/mL, at least about2300 ng·hr/mL, at least about 2400 ng·hr/mL, at least about 2500ng·hr/mL, at least about 2600 ng·hr/mL, at least about 2700 ng·hr/mL, atleast about 2800 ng·hr/mL, at least about 1850 ng·hr/mL, at least about2900 ng·hr/mL, at least about 2950 ng·hr/mL, or at least about 2975.3ng·hr/mL, and, in some embodiments, may be up to about 100,000 ng·hr/mL.

In some embodiments, the dextromethorphan AUC_(0-inf) on the tenth daythat the dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about75 ng·hr/mL, at least about 100 ng·hr/mL, at least about 200 ng·hr/mL,at least about 300 ng·hr/mL, at least about 400 ng·hr/mL, at least about500 ng·hr/mL, at least about 600 ng·hr/mL, at least about 700 ng·hr/mL,at least about 800 ng·hr/mL, at least about 900 ng·hr/mL, at least about1000 ng·hr/mL, at least about 1100 ng·hr/mL, at least about 1200ng·hr/mL, at least about 1300 ng·hr/mL, at least about 1400 ng·hr/mL, atleast about 1500 ng·hr/mL, at least about 1600 ng·hr/mL, at least about1700 ng·hr/mL, at least about 1800 ng·hr/mL, at least about 1900ng·hr/mL, at least about 2000 ng·hr/mL, at least about 2100 ng·hr/mL, atleast about 2200 ng·hr/mL, at least about 2300 ng·hr/mL, at least about2400 ng·hr/mL, at least about 2500 ng·hr/mL, at least about 2600ng·hr/mL, at least about 2700 ng·hr/mL, at least about 2800 ng·hr/mL, atleast about 2900 ng·hr/mL, at least about 3000 ng·hr/mL, at least about3100 ng·hr/mL, at least about 3200 ng·hr/mL, at least about 3300ng·hr/mL, at least about 3400 ng·hr/mL, at least about 3500 ng·hr/mL, atleast about 3600 ng·hr/mL, at least about 3700 ng·hr/mL, at least about3800 ng·hr/mL, at least about 3900 ng·hr/mL, at least about 4000ng·hr/mL, at least about 4100 ng·hr/mL, at least about 4200 ng·hr/mL, atleast about 4300 ng·hr/mL, at least about 4400 ng·hr/mL, at least about4500 ng·hr/mL, at least about 4600 ng·hr/mL, at least about 4700ng·hr/mL, at least about 4800 ng·hr/mL, at least about 4900 ng·hr/mL, atleast about 5000 ng·hr/mL, at least about 5100 ng·hr/mL, at least about5200 ng·hr/mL, at least about 5300 ng·hr/mL, at least about 5400ng·hr/mL, at least about 5500 ng·hr/mL, at least about 5600 ng·hr/mL, atleast about 5700 ng·hr/mL, at least about 5800 ng·hr/mL, at least about5900 ng·hr/mL, at least about 6000 ng·hr/mL, at least about 6100ng·hr/mL, at least about 6200 ng·hr/mL, at least about 6300 ng·hr/mL, atleast about 6400 ng·hr/mL, at least about 6500 ng·hr/mL, at least about6600 ng·hr/mL, at least about 6700 ng·hr/mL, at least about 6800ng·hr/mL, at least about 6900 ng·hr/mL, at least about 7000 ng·hr/mL, atleast about 7100 ng·hr/mL, at least about 7150 ng·hr/mL, at least about7200 ng·hr/mL, or at least about 7237.3 ng·hr/mL, and, in someembodiments, may be up to about 100,000 ng·hr/mL.

In some embodiments, the dextromethorphan C_(max) on the first day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least twicethe C_(max) that would be achieved by administering the same amount ofdextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextromethorphan C_(max) on the first day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.0 ng/mL, at least about 1.5 ng/mL, at least about 2.0 ng/mL, at leastabout 2.5 ng/mL, at least about 3.0 ng/mL, at least about 3.1 ng/mL, atleast about 3.2 ng/mL, at least about 3.3 ng/mL, at least about 3.4ng/mL, at least about 3.5 ng/mL, at least about 3.6 ng/mL, at leastabout 3.7 ng/mL, at least about 3.8 ng/mL, at least about 3.9 ng/mL, atleast about 4.0 ng/mL, at least about 4.1 ng/mL, at least about 4.2ng/mL, at least about 4.3 ng/mL, at least about 4.4 ng/mL, at leastabout 4.5 ng/mL, at least about 4.6 ng/mL, at least about 4.7 ng/mL, atleast about 4.8 ng/mL, at least about 4.9 ng/mL, at least about 5.0ng/mL, at least about 5.1 ng/mL, at least about 5.2 ng/mL, at leastabout 5.3 ng/mL, at least about 5.4 ng/mL, at least about 5.5 ng/mL, atleast about 5.6 ng/mL, at least about 5.7 ng/mL, at least about 5.8ng/mL, at least about 5.9 ng/mL, at least about 6.0 ng/mL, at leastabout 6.1 ng/mL, at least about 6.2 ng/mL, at least about 6.3 ng/mL, atleast about 6.4 ng/mL, at least about 6.5 ng/mL, at least about 6.6ng/mL, at least about 6.7 ng/mL, at least about 6.8 ng/mL, at leastabout 6.9 ng/mL, at least about 7.0 ng/mL, at least about 7.1 ng/mL, atleast about 7.2 ng/mL, at least about 7.3 ng/mL, at least about 7.4ng/mL, at least about 7.5 ng/mL, at least about 7.6 ng/mL, at leastabout 7.7 ng/mL, at least about 7.8 ng/mL, at least about 7.9 ng/mL, atleast about 8.0 ng/mL, at least about 8.1 ng/mL, at least about 8.2ng/mL, at least about 8.3 ng/mL, at least about 8.4 ng/mL, at leastabout 8.5 ng/mL, at least about 8.6 ng/mL, or at least about 8.7 ng/mL,and, in some embodiments, may be up to about 1000 ng·hr/mL.

In some embodiments, the dextromethorphan C_(max) on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be about 50 ng/mLto about 60 ng/mL, about 50 ng/mL to about 55 ng/mL, about 55 ng/mL toabout 60 ng/mL, about 80 ng/mL to about 90 ng/mL, about 80 ng/mL toabout 85 ng/mL, about 85 ng/mL to about 90 ng/mL, about 90 ng/mL toabout 95 ng/mL, about 95 ng/mL to about 100 ng/mL, about 100 ng/mL toabout 105 ng/mL, about 105 ng/mL to about 110 ng/mL, about 110 ng/mL toabout 115 ng/mL, about 115 ng/mL to about 120 ng/mL, about 120 ng/mL toabout 130 ng/mL, about 130 ng/mL to about 135 ng/mL, about 135 ng/mL toabout 140 ng/mL, about 140 ng/mL to about 145 ng/mL, about 145 ng/mL toabout 150 ng/mL, about 150 ng/mL to about 155 ng/mL, about 155 ng/mL toabout 160 ng/mL, about 160 ng/mL to about 170 ng/mL, about 170 ng/mL toabout 200 ng/mL, at least about 6.0 ng/mL, at least about 7.0 ng/mL, atleast about 8.0 ng/mL, at least about 9.0 ng/mL, at least about 10ng/mL, at least about 15 ng/mL, at least about 20 ng/mL, at least about25 ng/mL, at least about 30 ng/mL, at least about 35 ng/mL, at leastabout 40 ng/mL, at least about 45 ng/mL, at least about 50 ng/mL, atleast about 55 ng/mL, at least about 60 ng/mL, at least about 65 ng/mL,at least about 70 ng/mL, at least about 75 ng/mL, at least about 80ng/mL, at least about 85 ng/mL, at least about 90 ng/mL, at least about95 ng/mL, at least about 100 ng/mL, at least about 105 ng/mL, at leastabout 110 ng/mL, at least about 115 ng/mL, at least about 120 ng/mL, atleast about 125 ng/mL, at least about 130 ng/mL, at least about 135ng/mL, at least about 140 ng/mL, at least about 145 ng/mL, at leastabout 150 ng/mL, at least about 155 ng/mL, or at least about 158.1ng/mL, and, in some embodiments, may be up to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(max) on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be about 50 ng/mLto about 60 ng/mL, about 50 ng/mL to about 55 ng/mL, about 55 ng/mL toabout 60 ng/mL, about 80 ng/mL to about 90 ng/mL, about 80 ng/mL toabout 85 ng/mL, about 85 ng/mL to about 90 ng/mL, about 90 ng/mL toabout 95 ng/mL, about 95 ng/mL to about 100 ng/mL, about 100 ng/mL toabout 105 ng/mL, about 105 ng/mL to about 110 ng/mL, about 110 ng/mL toabout 115 ng/mL, about 115 ng/mL to about 120 ng/mL, about 120 ng/mL toabout 130 ng/mL, about 130 ng/mL to about 135 ng/mL, about 135 ng/mL toabout 140 ng/mL, about 140 ng/mL to about 145 ng/mL, about 145 ng/mL toabout 150 ng/mL, about 150 ng/mL to about 155 ng/mL, about 155 ng/mL toabout 160 ng/mL, about 160 ng/mL to about 170 ng/mL, about 170 ng/mL toabout 200 ng/mL, at least about 6.0 ng/mL, at least about 7.0 ng/mL, atleast about 8.0 ng/mL, at least about 9.0 ng/mL, at least about 10ng/mL, at least about 15 ng/mL, at least about 20 ng/mL, at least about25 ng/mL, at least about 30 ng/mL, at least about 35 ng/mL, at leastabout 40 ng/mL, at least about 45 ng/mL, at least about 50 ng/mL, atleast about 55 ng/mL, at least about 60 ng/mL, at least about 65 ng/mL,at least about 70 ng/mL, at least about 75 ng/mL, at least about 80ng/mL, at least about 85 ng/mL, at least about 90 ng/mL, at least about95 ng/mL, at least about 100 ng/mL, at least about 105 ng/mL, at leastabout 110 ng/mL, at least about 115 ng/mL, at least about 120 ng/mL, atleast about 125 ng/mL, at least about 130 ng/mL, at least about 135ng/mL, at least about 140 ng/mL, at least about 145 ng/mL, at leastabout 150 ng/mL, at least about 155 ng/mL, or at least about 158.1ng/mL, and, in some embodiments, may be up to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(max) on the tenth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be about 50 ng/mLto about 60 ng/mL, about 50 ng/mL to about 55 ng/mL, about 55 ng/mL toabout 60 ng/mL, about 80 ng/mL to about 90 ng/mL, about 80 ng/mL toabout 85 ng/mL, about 85 ng/mL to about 90 ng/mL, about 90 ng/mL toabout 95 ng/mL, about 95 ng/mL to about 100 ng/mL, about 100 ng/mL toabout 105 ng/mL, about 105 ng/mL to about 110 ng/mL, about 110 ng/mL toabout 115 ng/mL, about 115 ng/mL to about 120 ng/mL, about 120 ng/mL toabout 130 ng/mL, about 130 ng/mL to about 135 ng/mL, about 135 ng/mL toabout 140 ng/mL, about 140 ng/mL to about 145 ng/mL, about 145 ng/mL toabout 150 ng/mL, about 150 ng/mL to about 155 ng/mL, about 155 ng/mL toabout 160 ng/mL, about 160 ng/mL to about 170 ng/mL, about 170 ng/mL toabout 200 ng/mL, at least about 6.0 ng/mL, at least about 7.0 ng/mL, atleast about 8.0 ng/mL, at least about 9.0 ng/mL, at least about 10ng/mL, at least about 15 ng/mL, at least about 20 ng/mL, at least about25 ng/mL, at least about 30 ng/mL, at least about 35 ng/mL, at leastabout 40 ng/mL, at least about 45 ng/mL, at least about 50 ng/mL, atleast about 55 ng/mL, at least about 60 ng/mL, at least about 65 ng/mL,at least about 70 ng/mL, at least about 75 ng/mL, at least about 80ng/mL, at least about 85 ng/mL, at least about 90 ng/mL, at least about95 ng/mL, at least about 100 ng/mL, at least about 105 ng/mL, at leastabout 110 ng/mL, at least about 115 ng/mL, at least about 120 ng/mL, atleast about 125 ng/mL, at least about 130 ng/mL, at least about 135ng/mL, at least about 140 ng/mL, at least about 145 ng/mL, at leastabout 150 ng/mL, at least about 155 ng/mL, or at least about 158.1ng/mL, and, in some embodiments, may be up to about 10,000 ng/mL.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, is administered in an amount that results in a C_(avg) ofdextromethorphan, over the period between two separate and consecutiveadministrations of dextromethorphan, that is at least about 4.0 ng/mL,at least about 5.0 ng/mL, at least about 6.0 ng/mL, at least about 7.0ng/mL, at least about 8.0 ng/mL, at least about 9.0 ng/mL, at leastabout 10 ng/mL, at least about 15 ng/mL, at least about 20 ng/mL, atleast about 25 ng/mL, at least about 30 ng/mL, at least about 35 ng/mL,at least about 40 ng/mL, at least about 45 ng/mL, at least about 50ng/mL, at least about 55 ng/mL, at least about 60 ng/mL, at least about65 ng/mL, at least about 70 ng/mL, at least about 75 ng/mL, at leastabout 80 ng/mL, at least about 85 ng/mL, at least about 90 ng/mL, atleast about 95 ng/mL, at least about 100 ng/mL, at least about 105ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, at leastabout 120 ng/mL, at least about 125 ng/mL, at least about 130 ng/mL, atleast about 135 ng/mL, at least about 140 ng/mL, or at least about 140.5ng/mL, about 20 ng/mL to about 30 ng/mL, about 30 ng/mL to about 40ng/mL, about 40 ng/mL to about 50 ng/mL, about 50 ng/mL to about 55ng/mL, about 55 ng/mL to about 60 ng/mL, about 80 ng/mL to about 90ng/mL, about 80 ng/mL to about 85 ng/mL, about 85 ng/mL to about 90ng/mL, about 90 ng/mL to about 95 ng/mL, about 95 ng/mL to about 100ng/mL, about 100 ng/mL to about 105 ng/mL, about 105 ng/mL to about 110ng/mL, about 110 ng/mL to about 115 ng/mL, about 115 ng/mL to about 120ng/mL, about 120 ng/mL to about 130 ng/mL, about 130 ng/mL to about 135ng/mL, about 135 ng/mL to about 140 ng/mL, about 140 ng/mL to about 145ng/mL, about 145 ng/mL to about 150 ng/mL, about 150 ng/mL to about 155ng/mL, about 155 ng/mL to about 160 ng/mL, about 160 ng/mL to about 170ng/mL, about 170 ng/mL to about 200 ng/mL, and, in some embodiments, maybe up to about 10,000 ng/mL. For example, if dextromethorphan isadministered at 8 am and at 8 pm on day 1, and no dextromethorphan isadministered after 8 am and before 8 pm on day 1, the period between twoseparate and consecutive administrations of dextromethorphan is fromimmediately after 8 am to immediately before 8 pm on day 1.

In some embodiments, the dextromethorphan C_(avg) on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, at leastabout 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0 ng/mL, atleast about 10 ng/mL, at least about 15 ng/mL, at least about 20 ng/mL,at least about 25 ng/mL, at least about 30 ng/mL, at least about 35ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, at least about50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL, at leastabout 65 ng/mL, at least about 70 ng/mL, at least about 75 ng/mL, atleast about 80 ng/mL, at least about 85 ng/mL, at least about 90 ng/mL,at least about 95 ng/mL, at least about 100 ng/mL, at least about 105ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, at leastabout 120 ng/mL, at least about 125 ng/mL, at least about 130 ng/mL, atleast about 135 ng/mL, at least about 140 ng/mL, or at least about 140.5ng/mL, about 20 ng/mL to about 30 ng/mL, about 30 ng/mL to about 40ng/mL, about 40 ng/mL to about 50 ng/mL, about 50 ng/mL to about 55ng/mL, about 55 ng/mL to about 60 ng/mL, about 80 ng/mL to about 90ng/mL, about 80 ng/mL to about 85 ng/mL, about 85 ng/mL to about 90ng/mL, about 90 ng/mL to about 95 ng/mL, about 95 ng/mL to about 100ng/mL, about 100 ng/mL to about 105 ng/mL, about 105 ng/mL to about 110ng/mL, about 110 ng/mL to about 115 ng/mL, about 115 ng/mL to about 120ng/mL, about 120 ng/mL to about 130 ng/mL, about 130 ng/mL to about 135ng/mL, about 135 ng/mL to about 140 ng/mL, about 140 ng/mL to about 145ng/mL, about 145 ng/mL to about 150 ng/mL, about 150 ng/mL to about 155ng/mL, about 155 ng/mL to about 160 ng/mL, about 160 ng/mL to about 170ng/mL, about 170 ng/mL to about 200 ng/mL, and, in some embodiments, maybe up to about 10,000 ng/mL. The C_(avg) values given above can be forthe period between two separate and consecutive administrations ofdextromethorphan, or if dextromethorphan is administered only once onDay 8, the C_(avg) can be for 12 hours after the first dose ofdextromethorphan.

In some embodiments, the dextromethorphan C_(avg) on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, at leastabout 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0 ng/mL, atleast about 10 ng/mL, at least about 15 ng/mL, at least about 20 ng/mL,at least about 25 ng/mL, at least about 30 ng/mL, at least about 35ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, at least about50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL, at leastabout 65 ng/mL, at least about 70 ng/mL, at least about 75 ng/mL, atleast about 80 ng/mL, at least about 85 ng/mL, at least about 90 ng/mL,at least about 95 ng/mL, at least about 100 ng/mL, at least about 105ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, at leastabout 120 ng/mL, at least about 125 ng/mL, at least about 130 ng/mL, atleast about 135 ng/mL, at least about 140 ng/mL, or at least about 140.5ng/mL, about 20 ng/mL to about 30 ng/mL, about 30 ng/mL to about 40ng/mL, about 40 ng/mL to about 50 ng/mL, about 50 ng/mL to about 55ng/mL, about 55 ng/mL to about 60 ng/mL, about 80 ng/mL to about 90ng/mL, about 80 ng/mL to about 85 ng/mL, about 85 ng/mL to about 90ng/mL, about 90 ng/mL to about 95 ng/mL, about 95 ng/mL to about 100ng/mL, about 100 ng/mL to about 105 ng/mL, about 105 ng/mL to about 110ng/mL, about 110 ng/mL to about 115 ng/mL, about 115 ng/mL to about 120ng/mL, about 120 ng/mL to about 130 ng/mL, about 130 ng/mL to about 135ng/mL, about 135 ng/mL to about 140 ng/mL, about 140 ng/mL to about 145ng/mL, about 145 ng/mL to about 150 ng/mL, about 150 ng/mL to about 155ng/mL, about 155 ng/mL to about 160 ng/mL, about 160 ng/mL to about 170ng/mL, about 170 ng/mL to about 200 ng/mL, and, in some embodiments, maybe up to about 10,000 ng/mL. The C_(avg) values given above can be forthe period between two separate and consecutive administrations ofdextromethorphan, or if dextromethorphan is administered only once onDay 9, the C_(avg) can be for 12 hours after the first dose ofdextromethorphan.

In some embodiments, the dextromethorphan C_(avg) on the tenth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, at leastabout 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0 ng/mL, atleast about 10 ng/mL, at least about 15 ng/mL, at least about 20 ng/mL,at least about 25 ng/mL, at least about 30 ng/mL, at least about 35ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, at least about50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL, at leastabout 65 ng/mL, at least about 70 ng/mL, at least about 75 ng/mL, atleast about 80 ng/mL, at least about 85 ng/mL, at least about 90 ng/mL,at least about 95 ng/mL, at least about 100 ng/mL, at least about 105ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, at leastabout 120 ng/mL, at least about 125 ng/mL, at least about 130 ng/mL, atleast about 135 ng/mL, at least about 140 ng/mL, or at least about 140.5ng/mL, about 20 ng/mL to about 30 ng/mL, about 30 ng/mL to about 40ng/mL, about 40 ng/mL to about 50 ng/mL, about 50 ng/mL to about 55ng/mL, about 55 ng/mL to about 60 ng/mL, about 80 ng/mL to about 90ng/mL, about 80 ng/mL to about 85 ng/mL, about 85 ng/mL to about 90ng/mL, about 90 ng/mL to about 95 ng/mL, about 95 ng/mL to about 100ng/mL, about 100 ng/mL to about 105 ng/mL, about 105 ng/mL to about 110ng/mL, about 110 ng/mL to about 115 ng/mL, about 115 ng/mL to about 120ng/mL, about 120 ng/mL to about 130 ng/mL, about 130 ng/mL to about 135ng/mL, about 135 ng/mL to about 140 ng/mL, about 140 ng/mL to about 145ng/mL, about 145 ng/mL to about 150 ng/mL, about 150 ng/mL to about 155ng/mL, about 155 ng/mL to about 160 ng/mL, about 160 ng/mL to about 170ng/mL, about 170 ng/mL to about 200 ng/mL, and, in some embodiments, maybe up to about 10,000 ng/mL. The C_(avg) values given above can be forthe period between two separate and consecutive administrations ofdextromethorphan, or if dextromethorphan is administered only once onDay 10, the C_(avg) can be for 12 hours after the first dose ofdextromethorphan.

The dextromethorphan fluctuation index values FI (%) can be determinedby equation:

${{FI}\mspace{11mu}(\%)} = {\frac{\left( {C_{\max} - C_{\min}} \right)}{C_{avg}} \times 100.}$

In some embodiments, the dextromethorphan FI (%) on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is reduced by at least 1.5-fold or atleast 2-fold as compared to dextromethorphan that is administered foreight days without plasma level enhancement, such as byco-administration of dextromethorphan with of bupropion,hydroxybupropion, threohydroxybupropion, erythrohydroxybupropion, or ametabolite or prodrug of any of these compounds.

In some embodiments, the dextromethorphan FI (%) on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is reduced by at least 1.5-fold or atleast 2-fold as compared to dextromethorphan that is administered fornine days without plasma level enhancement, such as by co-administrationof dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextromethorphan FI (%) on the tenth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is reduced by at least 1.5-fold or atleast 2-fold as compared to dextromethorphan that is administered forten days without plasma level enhancement, such as by co-administrationof dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextromethorphan FI (%) on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is less than 100%, less than 50%,less than 40%, less than 30%, about 20-50%, about 20-40%, about 20-30%,or any FI (%) value in a range bounded by any of these values.

In some embodiments, the dextromethorphan FI (%) on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is less than 100%, less than 50%,less than 40%, less than 30%, about 20-50%, about 20-40%, about 20-30%,or any FI (%) value in a range bounded by any of these values.

In some embodiments, the dextromethorphan FI (%) on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is less than 100%, less than 50%,less than 40%, less than 30%, about 20-50%, about 20-40%, about 20-30%,or any FI (%) value in a range bounded by any of these values.

In some embodiments, the dextrorphan FI (%) on the eighth day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is reduced by at least 1.5-fold, atleast 2-fold, at least 3-fold, at least 4-fold, at least 5-fold, or atleast 6-fold as compared to dextromethorphan that is administered foreight days without plasma level enhancement, such as byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextrorphan FI (%) on the ninth day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is reduced by at least 1.5-fold, atleast 2-fold, at least 3-fold, at least 4-fold, at least 5-fold, or atleast 6-fold as compared to dextromethorphan that is administered fornine days without plasma level enhancement, such as by co-administrationof dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextrorphan FI (%) on the tenth day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is reduced by at least 1.5-fold, atleast 2-fold, at least 3-fold, at least 4-fold, at least 5-fold, or atleast 6-fold as compared to dextromethorphan that is administered forten days without plasma level enhancement, such as by co-administrationof dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextrorphan FI (%) on the eighth day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is less than 100%, less than 70%,less than 60%, less than 50%, about 30-70%, about 30-60%, about 30-50%,or any FI (%) value in a range bounded by any of these values.

In some embodiments, the dextrorphan FI (%) on the ninth day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is less than 100%, less than 70%,less than 60%, less than 50%, about 30-70%, about 30-60%, about 30-50%,or any FI (%) value in a range bounded by any of these values.

In some embodiments, the dextrorphan FI (%) on the ninth day that thedextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is less than 100%, less than 70%,less than 60%, less than 50%, about 30-70%, about 30-60%, about 30-50%,or any FI (%) value in a range bounded by any of these values.

In some embodiments, the dextromethorphan trough level (e.g. plasmalevel 12 hours after administration; also referred herein as “C_(min)”)on the first day that bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least twicethe trough level that would be achieved by administering the same amountof dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds.

In some embodiments, the dextromethorphan C_(min) on the first day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about0.8 ng/mL, at least about 0.9 ng/mL, at least about 1.0 ng/mL, at leastabout 1.1 ng/mL, at least about 1.2 ng/mL, at least about 1.3 ng/mL, atleast about 1.4 ng/mL, at least about 1.5 ng/mL, at least about 1.6ng/mL, at least about 1.7 ng/mL, at least about 1.8 ng/mL, at leastabout 1.9 ng/mL, at least about 2.0 ng/mL, at least about 2.1 ng/mL, atleast about 2.2 ng/mL, at least about 2.3 ng/mL, at least about 2.4ng/mL, at least about 2.5 ng/mL, or at least about 2.5 ng/mL, and may beup to about 100 ng/mL.

In some embodiments, the dextromethorphan C_(min) on the fifth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.5 ng/mL, at least about 2.0 ng/mL, at least about 3.0 ng/mL, at leastabout 4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, atleast about 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0ng/mL, at least about 10 ng/mL, at least about 15 ng/mL, at least about20 ng/mL, at least about 25 ng/mL, at least about 30 ng/mL, at leastabout 35 ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, atleast about 50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL,at least about 65 ng/mL, at least about 70 ng/mL, at least about 75ng/mL, at least about 80 ng/mL, or at least about 80.9 ng/mL, and may beup to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(min) on the sixth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.5 ng/mL, at least about 2.0 ng/mL, at least about 3.0 ng/mL, at leastabout 4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, atleast about 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0ng/mL, at least about 10 ng/mL, at least about 15 ng/mL, at least about20 ng/mL, at least about 25 ng/mL, at least about 30 ng/mL, at leastabout 35 ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, atleast about 50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL,at least about 65 ng/mL, at least about 70 ng/mL, at least about 75ng/mL, at least about 80 ng/mL, at least about 85 ng/mL, at least about90 ng/mL, at least about 95 ng/mL, at least about 100 ng/mL, or at leastabout 102.2 ng/mL, and may be up to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(min) on the seventh daythat the dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.5 ng/mL, at least about 2.0 ng/mL, at least about 3.0 ng/mL, at leastabout 4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, atleast about 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0ng/mL, at least about 10 ng/mL, at least about 15 ng/mL, at least about20 ng/mL, at least about 25 ng/mL, at least about 30 ng/mL, at leastabout 35 ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, atleast about 50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL,at least about 65 ng/mL, at least about 70 ng/mL, at least about 75ng/mL, at least about 80 ng/mL, at least about 85 ng/mL, at least about90 ng/mL, at least about 95 ng/mL, at least about 100 ng/mL, at leastabout 105 ng/mL, at least about 110 ng/mL, or at least about 110.6ng/mL, and may be up to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(min) on the eighth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.5 ng/mL, at least about 2.0 ng/mL, at least about 3.0 ng/mL, at leastabout 4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, atleast about 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0ng/mL, at least about 10 ng/mL, at least about 15 ng/mL, at least about20 ng/mL, at least about 25 ng/mL, at least about 30 ng/mL, at leastabout 35 ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, atleast about 50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL,at least about 65 ng/mL, at least about 70 ng/mL, at least about 75ng/mL, at least about 80 ng/mL, at least about 85 ng/mL, at least about90 ng/mL, at least about 95 ng/mL, at least about 100 ng/mL, at leastabout 105 ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, atleast about 119.3 ng/mL, about 20 ng/mL to about 30 ng/mL, about 30ng/mL to about 40 ng/mL, about 40 ng/mL to about 50 ng/mL, about 50ng/mL to about 55 ng/mL, about 55 ng/mL to about 60 ng/mL, about 80ng/mL to about 90 ng/mL, about 80 ng/mL to about 85 ng/mL, about 85ng/mL to about 90 ng/mL, about 90 ng/mL to about 95 ng/mL, about 95ng/mL to about 100 ng/mL, about 100 ng/mL to about 105 ng/mL, about 105ng/mL to about 110 ng/mL, about 110 ng/mL to about 115 ng/mL, about 115ng/mL to about 120 ng/mL, about 120 ng/mL to about 130 ng/mL, about 130ng/mL to about 135 ng/mL, about 135 ng/mL to about 140 ng/mL, about 140ng/mL to about 145 ng/mL, about 145 ng/mL to about 150 ng/mL, about 150ng/mL to about 155 ng/mL, about 155 ng/mL to about 160 ng/mL, about 160ng/mL to about 170 ng/mL, or about 170 ng/mL to about 200 ng/mL, and maybe up to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(min) on the ninth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.5 ng/mL, at least about 2.0 ng/mL, at least about 3.0 ng/mL, at leastabout 4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, atleast about 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0ng/mL, at least about 10 ng/mL, at least about 15 ng/mL, at least about20 ng/mL, at least about 25 ng/mL, at least about 30 ng/mL, at leastabout 35 ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, atleast about 50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL,at least about 65 ng/mL, at least about 70 ng/mL, at least about 75ng/mL, at least about 80 ng/mL, at least about 85 ng/mL, at least about90 ng/mL, at least about 95 ng/mL, at least about 100 ng/mL, at leastabout 105 ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, atleast about 119.3 ng/mL, about 20 ng/mL to about 30 ng/mL, about 30ng/mL to about 40 ng/mL, about 40 ng/mL to about 50 ng/mL, about 50ng/mL to about 55 ng/mL, about 55 ng/mL to about 60 ng/mL, about 80ng/mL to about 90 ng/mL, about 80 ng/mL to about 85 ng/mL, about 85ng/mL to about 90 ng/mL, about 90 ng/mL to about 95 ng/mL, about 95ng/mL to about 100 ng/mL, about 100 ng/mL to about 105 ng/mL, about 105ng/mL to about 110 ng/mL, about 110 ng/mL to about 115 ng/mL, about 115ng/mL to about 120 ng/mL, about 120 ng/mL to about 130 ng/mL, about 130ng/mL to about 135 ng/mL, about 135 ng/mL to about 140 ng/mL, about 140ng/mL to about 145 ng/mL, about 145 ng/mL to about 150 ng/mL, about 150ng/mL to about 155 ng/mL, about 155 ng/mL to about 160 ng/mL, about 160ng/mL to about 170 ng/mL, or about 170 ng/mL to about 200 ng/mL, and maybe up to about 10,000 ng/mL.

In some embodiments, the dextromethorphan C_(min) on the tenth day thatthe dextromethorphan plasma level is enhanced, for example byco-administration of dextromethorphan with bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, is administered may be at least about1.5 ng/mL, at least about 2.0 ng/mL, at least about 3.0 ng/mL, at leastabout 4.0 ng/mL, at least about 5.0 ng/mL, at least about 6.0 ng/mL, atleast about 7.0 ng/mL, at least about 8.0 ng/mL, at least about 9.0ng/mL, at least about 10 ng/mL, at least about 15 ng/mL, at least about20 ng/mL, at least about 25 ng/mL, at least about 30 ng/mL, at leastabout 35 ng/mL, at least about 40 ng/mL, at least about 45 ng/mL, atleast about 50 ng/mL, at least about 55 ng/mL, at least about 60 ng/mL,at least about 65 ng/mL, at least about 70 ng/mL, at least about 75ng/mL, at least about 80 ng/mL, at least about 85 ng/mL, at least about90 ng/mL, at least about 95 ng/mL, at least about 100 ng/mL, at leastabout 105 ng/mL, at least about 110 ng/mL, at least about 115 ng/mL, atleast about 119.3 ng/mL, about 20 ng/mL to about 30 ng/mL, about 30ng/mL to about 40 ng/mL, about 40 ng/mL to about 50 ng/mL, about 50ng/mL to about 55 ng/mL, about 55 ng/mL to about 60 ng/mL, about 80ng/mL to about 90 ng/mL, about 80 ng/mL to about 85 ng/mL, about 85ng/mL to about 90 ng/mL, about 90 ng/mL to about 95 ng/mL, about 95ng/mL to about 100 ng/mL, about 100 ng/mL to about 105 ng/mL, about 105ng/mL to about 110 ng/mL, about 110 ng/mL to about 115 ng/mL, about 115ng/mL to about 120 ng/mL, about 120 ng/mL to about 130 ng/mL, about 130ng/mL to about 135 ng/mL, about 135 ng/mL to about 140 ng/mL, about 140ng/mL to about 145 ng/mL, about 145 ng/mL to about 150 ng/mL, about 150ng/mL to about 155 ng/mL, about 155 ng/mL to about 160 ng/mL, about 160ng/mL to about 170 ng/mL, or about 170 ng/mL to about 200 ng/mL, and maybe up to about 10,000 ng/mL.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, is administered on the first day of at least two days oftreatment with dextromethorphan, wherein a decrease in the dextrorphanplasma level occurs on the first day that bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, and dextromethorphan areco-administered, as compared to the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds. For example, the dextrorphan plasma level on the first daymay be reduced by at least 5% as compared to the dextrorphan plasmalevel that would be achieved by administering the same amount ofdextromethorphan without bupropion.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, are co-administered with dextromethorphan for at least fiveconsecutive days, to a human being in need of treatment withdextromethorphan, wherein, on the fifth day, the dextromethorphan plasmalevel is higher than the dextromethorphan plasma level that would havebeen achieved by administering the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, for five consecutive days. For example, the dextromethorphanplasma level on the fifth day (for example at 0 hours, 1 hour, 3 hours,6 hours, or 12 hours after administration) may be at least 5 times, atleast 10 times, at least 20 times, at least 40 times, at least 50 times,at least 60 times, at least 65 times, or up to about 500 times, thelevel that would be achieved by administering the same amount ofdextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for five consecutive days.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan, are co-administered for at least sixconsecutive days, to a human being in need of treatment withdextromethorphan, wherein, on the sixth day, the dextromethorphan plasmalevel is higher than the dextromethorphan plasma level that would havebeen achieved by administering the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, for six consecutive days. For example, the dextromethorphanplasma level on the sixth day (for example at 0 hours, 1 hour, 3 hours,6 hours, or 12 hours after administration) may be at least 5 times, atleast 10 times, at least 20 times, at least 30 times, at least 50 times,at least 60 times, at least 70 times, at least 75 times, or up to about500 times, the level that would be achieved by administering the sameamount of dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for six consecutive days.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan, are co-administered for at least sevenconsecutive days, to a human being in need of treatment withdextromethorphan, wherein, on the seventh day, the dextromethorphanplasma level is higher than the dextromethorphan plasma level that wouldhave been achieved by administering the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, for seven consecutive days. For example, the dextromethorphanplasma level on the seventh day (for example at 0 hours, 1 hour, 3hours, 6 hours, or 12 hours after administration) may be at least 5times, at least 10 times, at least 20 times, at least 30 times, at least50 times, at least 70 times, at least 80 times, at least 90 times, or upto about 500 times, the level that would be achieved by administeringthe same amount of dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for seven consecutive days.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan, are co-administered for at least eightconsecutive days, wherein, on the eighth day, dextromethorphan has aplasma level, for example at 0 hours, 1 hour, 3 hours, 6 hours, or 12hours, after co-administering bupropion with dextromethorphan that is atleast 5 times, at least 10 times, at least 20 times, at least 30 times,at least 50 times, at least 60 times, at least 70 times, at least 80times, at least 90 times, at least 100 times, or up to about 1,000times, the plasma level that would be achieved by administering the sameamount of dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for eight consecutive days.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan are co-administered for at least eightconsecutive days, to a human being in need of treatment withdextromethorphan, wherein, on the eighth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, for eight consecutive days. For example, the dextrorphanplasma level on the eighth day (for example at 0 hours, 1 hour, 3 hours,6 hours, or 12 hours after administration) may be reduced by at least10%, at least 20%, at least 30%, at least 40%, or at least 50%, ascompared to the dextrorphan plasma level that would be achieved byadministering the same amount of dextromethorphan without bupropion,hydroxybupropion, threohydroxybupropion, erythrohydroxybupropion, or ametabolite or prodrug of any of these compounds, for eight consecutivedays.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan, are co-administered for at least nineconsecutive days, wherein, on the ninth day, dextromethorphan has aplasma level, for example at 0 hours, 1 hour, 3 hours, 6 hours, or 12hours, after co-administering bupropion with dextromethorphan that is atleast 5 times, at least 10 times, at least 20 times, at least 30 times,at least 50 times, at least 60 times, at least 70 times, at least 80times, at least 90 times, at least 100 times, or up to about 1,000times, the plasma level that would be achieved by administering the sameamount of dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for nine consecutive days.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan are co-administered for at least nineconsecutive days, to a human being in need of treatment withdextromethorphan, wherein, on the ninth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, for nine consecutive days. For example, the dextrorphanplasma level on the ninth day (for example at 0 hours, 1 hour, 3 hours,6 hours, or 12 hours after administration) may be reduced by at least10%, at least 20%, at least 30%, at least 40%, or at least 50%, ascompared to the dextrorphan plasma level that would be achieved byadministering the same amount of dextromethorphan without bupropion,hydroxybupropion, threohydroxybupropion, erythrohydroxybupropion, or ametabolite or prodrug of any of these compounds, for nine consecutivedays.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan, are co-administered for at least tenconsecutive days, wherein, on the tenth day, dextromethorphan has aplasma level, for example at 0 hours, 1 hour, 3 hours, 6 hours, or 12hours, after co-administering bupropion with dextromethorphan that is atleast 5 times, at least 10 times, at least 20 times, at least 30 times,at least 50 times, at least 60 times, at least 70 times, at least 80times, at least 90 times, at least 100 times, or up to about 1,000times, the plasma level that would be achieved by administering the sameamount of dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for ten consecutive days.

In some embodiments, bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, and dextromethorphan are co-administered for at least tenconsecutive days, to a human being in need of treatment withdextromethorphan, wherein, on the tenth day, the dextrorphan plasmalevel is lower than the dextrorphan plasma level that would have beenachieved by administering the same amount of dextromethorphanadministered without bupropion, hydroxybupropion, threohydroxybupropion,erythrohydroxybupropion, or a metabolite or prodrug of any of thesecompounds, for ten consecutive days. For example, the dextrorphan plasmalevel on the tenth day (for example at 0 hours, 1 hour, 3 hours, 6hours, or 12 hours after administration) may be reduced by at least 10%,at least 20%, at least 30%, at least 40%, or at least 50%, as comparedto the dextrorphan plasma level that would be achieved by administeringthe same amount of dextromethorphan without bupropion, hydroxybupropion,threohydroxybupropion, erythrohydroxybupropion, or a metabolite orprodrug of any of these compounds, for ten consecutive days.

In some embodiments, bupropion may be administered to a human being inan amount that results in an AUC₀₋₁₂ of bupropion in the human being, onday 8, that is at least about 100 ng·hr/mL, at least about 200 ng·hr/mL,at least about 500 ng·hr/mL, at least about 600 ng·hr/mL, at least about700 ng·hr/mL, at least about 800 ng·hr/mL, at least about 900 ng·hr/mL,at least about 1,000 ng·hr/mL, at least about 1,200 ng·hr/mL, at least1,600 ng·hr/mL, or up to about 15,000 ng·hr/mL.

In some embodiments, bupropion may be administered to a human being inan amount that results in a C_(avg) of bupropion in the human being, onday 8, that is at least about 10 ng/mL, at least about 20 ng/mL, atleast about 40 ng/mL, at least about 50 ng/mL, at least about 60 ng/mL,at least about 70 ng/mL, at least about 80 ng/mL, at least about 90ng/mL, at least about 100 ng/mL, at least 120 ng/mL, or up to about1,500 ng/mL.

In some embodiments, bupropion may be administered to a human being inan amount that results in a C_(max) of bupropion in the human being, onday 8, that is at least about 10 ng/mL, at least about 20 ng/mL, atleast about 50 ng/mL, at least about 90 ng/mL, at least about 100 ng/mL,at least about 110 ng/mL, at least about 120 ng/mL, at least about 130ng/mL, at least about 140 ng/mL, at least 200 ng/mL, or up to about1,500 ng/mL.

Some liquid compositions may comprise about 0.0001% (w/v) to about 50%(w/v), about 0.01% (w/v) to about 20% (w/v), about 0.01% to about 10%(w/v), about 1% (w/v) to about 3% (w/v), about 3% (w/v) to about 5%(w/v), about 5% (w/v) to about 7% (w/v), about 5% (w/v) to about 15%(w/v), about 7% (w/v) to about 10% (w/v), about 10% (w/v) to about 15%(w/v), about 15% (w/v) to about 20% (w/v), about 20% (w/v) to about 30%(w/v), about 30% (w/v) to about 40% (w/v), or about 40% (w/v) to about50% (w/v) of bupropion, or any amount of bupropion in a range boundedby, or between, any of these values.

Some liquid dosage forms may contain about 10 mg to about 1000 mg, about50 mg to about 1000 mg, about 10 mg to about 50 mg, about 50 mg to about100 mg, about 40 mg to about 90 mg, about 200 mg to about 300 mg, about70 mg to about 95 mg, about 100 mg to about 200 mg, about 100 mg toabout 110 mg, about 105 mg to about 200 mg, about 110 mg to about 140mg, about 180 mg to about 220 mg, about 280 mg to about 320 mg, about105 mg, about 200 mg, about 150 mg, or about 300 mg of bupropion, e.g.bupropion chloride, or any amount of bupropion in a range bounded by, orbetween, any of these values.

Some solid compositions may comprise at least about 5% (w/w), at leastabout 10% (w/w), at least about 20% (w/w), at least about 50% (w/w), atleast about 70% (w/w), at least about 80%, about 10% (w/w) to about 30%(w/w), about 10% (w/w) to about 20% (w/w), about 20% (w/w) to about 30%(w/w), about 30% (w/w) to about 50% (w/w), about 30% (w/w) to about 40%(w/w), about 40% (w/w) to about 50% (w/w), about 50% (w/w) to about 80%(w/w), about 50% (w/w) to about 60% (w/w), about 70% (w/w) to about 80%(w/w), or about 80% (w/w) to about 90% (w/w) of bupropion, or any amountof bupropion in a range bounded by, or between, any of these values.

Some solid dosage forms may contain about 10 mg to about 1000 mg, about50 mg to about 1000 mg, about 10 mg to about 50 mg, about 50 mg to about100 mg, about 40 mg to about 90 mg, about 200 mg to about 300 mg, about70 mg to about 95 mg, about 100 mg to about 200 mg, about 100 mg toabout 120 mg, about 105 mg to about 200 mg, about 90 mg to about 120 mg,about 100 mg to about 110 mg, about 110 mg to about 140 mg, about 50 mgto about 150 mg, about 180 mg to about 220 mg, about 280 mg to about 320mg, about 105 mg, about 200 mg, about 150 mg, or about 300 mg ofbupropion, e.g. bupropion chloride, or any amount of bupropion in arange bounded by, or between, any of these values.

In some embodiments, bupropion is administered at a dose that results ina bupropion plasma level of about 0.1 μM to about 10 μM, about 0.1 μM toabout 5 μM, about 0.2 μM to about 3 μM, about 0.1 μM to about 1 μM,about 0.2 μM to about 2 μM, about 1 μM to about 10 μM, about 1 μM toabout 5 μM, about 2 μM to about 3 μM, or about 2.8 μM to about 3 μM,about 1.5 μM to about 2 μM, about 4.5 μM to about 5 μM, about 2.5 μM toabout 3 μM, about 1.8 μM, about 4.8 μM, about 2.9 μM, about 2.8 μM, orany plasma level in a range bounded by, or between, any of these values.

In some embodiments, bupropion, hydroxybupropion, or a prodrug ofhydroxybupropion, is administered at a dose that results in ahydroxybupropion plasma level of about 0.1 μM to about 10 μM, about 0.1μM to about 5 μM, about 0.2 μM to about 3 μM, about 0.1 μM to about 1μM, about 0.2 μM to about 2 μM, 1 μM to about 10 μM, about 1 μM to about5 μM, about 2 μM to about 3 μM, or about 2.8 μM to about 3 μM, about 1.5μM to about 2 μM, about 4.5 μM to about 5 μM, about 2.5 μM to about 3μM, about 1.8 μM, about 4.8 μM, about 2.9 μM, about 2.8 μM, or anyplasma level in a range bounded by, or between, any of these values.

In some embodiments, bupropion, hydroxybupropion, or a prodrug ofhydroxybupropion, may be administered to a human being in an amount thatresults in an AUC₀₋₁₂ of hydroxybupropion in the human being, on day 8,that is at least about 3,000 ng·hr/mL, at least about 7,000 ng·hr/mL, atleast about 10,000 ng·hr/mL, at least about 15,000 ng·hr/mL, at leastabout 20,000 ng·hr/mL, at least about 30,000 ng·hr/mL, up to about50,000 ng·hr/mL, up to about 150,000 ng·hr/mL, or any AUC in a rangebounded by, or between, any of these values.

In some embodiments, bupropion, hydroxybupropion, or a prodrug ofhydroxybupropion, may be administered to a human being in an amount thatresults in a C_(max) of hydroxybupropion in the human being, on day 8,that is at least about 300 ng/mL, at least about 700 ng/mL, at leastabout 1,000 ng/mL, at least about 1,500 ng/mL, at least about 2,000ng/mL, at least about 4,000 ng/mL, up to about 10,000 ng/mL, up to about50,000 ng/mL, or any C_(max) in a range bounded by, or between, any ofthese values.

In some embodiments, bupropion, hydroxybupropion, or a prodrug ofhydroxybupropion, may be administered to a human being in an amount thatresults in a C_(avg) of hydroxybupropion in the human being, on day 8,that is at least about 200 ng/mL, at least about 300 ng/mL, at leastabout 700 ng/mL, at least about 1,000 ng/mL, at least about 1,500 ng/mL,at least about 2,000 ng/mL, at least about 4,000 ng/mL, up to about10,000 ng/mL, up to about 50,000 ng/mL, or any C_(avg) in a rangebounded by, or between, any of these values.

In some embodiments, bupropion, threohydroxybupropion, or a prodrug ofthreohydroxybupropion, is administered at a dose that results in athreohydroxybupropion plasma level of about 0.1 μM to about 10 μM, about0.1 μM to about 5 μM, about 0.2 μM to about 3 μM, about 0.1 μM to about1 μM, about 0.2 μM to about 2 μM, about 1 μM to about 10 μM, about 1 μMto about 5 μM, about 2 μM to about 3 μM, or about 2.8 μM to about 3 μM,about 1.5 μM to about 2 μM, about 4.5 μM to about 5 μM, about 2.5 μM toabout 3 μM, about 1.8 μM, about 4.8 μM, about 2.9 μM, about 2.8 μM, orany plasma level in a range bounded by, or between, any of these values.

In some embodiments, bupropion, threohydroxybupropion, or a prodrug ofthreohydroxybupropion, may be administered to a human being in an amountthat results in an AUC₀₋₁₂ of threohydroxybupropion in the human being,on day 8, that is at least about 1,000 ng·hr/mL, at least about 2,000ng·hr/mL, at least about 4,000 ng·hr/mL, at least about 5,000 ng·hr/mL,at least about 8,000 ng·hr/mL, up to about 10,000 ng·hr/mL, up to about40,000 ng·hr/mL, or any AUC in a range bounded by, or between, any ofthese values.

In some embodiments, bupropion, threohydroxybupropion, or a prodrug ofthreohydroxybupropion, may be administered to a human being in an amountthat results in a C_(max) of threohydroxybupropion in the human being,on day 8, that is at least about 100 ng/mL, at least about 200 ng/mL, atleast about 400 ng/mL, at least about 500 ng/mL, at least about 600ng/mL, at least about 800 ng/mL, up to about 2,000 ng/mL, up to about10,000 ng/mL, or any C_(max) in a range bounded by, or between, any ofthese values.

In some embodiments, bupropion, threohydroxybupropion, or a prodrug ofthreohydroxybupropion, may be administered to a human being in an amountthat results in a C_(avg) of threohydroxybupropion in the human being,on day 8, that is at least about 100 ng/mL, at least about 300 ng/mL, atleast about 400 ng/mL, at least about 600 ng/mL, at least about 800ng/mL, up to about 2,000 ng/mL, up to about 10,000 ng/mL, or any C_(avg)in a range bounded by, or between, any of these values.

In some embodiments, bupropion, erythrohydroxybupropion, or a prodrug oferythrohydroxybupropion, is administered at a dose that results in anerythrohydroxybupropion plasma level of about 0.1 μM to about 10 μM,about 0.1 μM to about 5 μM, about 0.2 μM to about 3 μM, about 0.1 μM toabout 1 μM, about 0.2 μM to about 2 μM, about 1 μM to about 10 μM, about1 μM to about 5 μM, about 2 μM to about 3 μM, or about 2.8 μM to about 3μM, about 1.5 μM to about 2 μM, about 4.5 μM to about 5 μM, about 2.5 μMto about 3 μM, about 1.8 μM, about 4.8 μM, about 2.9 μM, about 2.8 μM,or any plasma level in a range bounded by, or between, any of thesevalues.

In some embodiments, bupropion, erythrohydroxybupropion, or a prodrug oferythrohydroxybupropion, may be administered to a human being in anamount that results in an AUC₀₋₁₂ of erythrohydroxybupropion in thehuman being, on day 8, that is at least about 200 ng·hr/mL, at leastabout 400 ng·hr/mL, at least about 700 ng·hr/mL, at least about 1,000ng·hr/mL, at least about 1,500 ng·hr/mL, at least about 3,000 ng·hr/mL,up to about 5,000 ng·hr/mL, up to about 30,000 ng·hr/mL, or any plasmalevel in a range bounded by, or between, any of these values.

In some embodiments, bupropion, erythrohydroxybupropion, or a prodrug oferythrohydroxybupropion, may be administered to a human being in anamount that results in a C_(max) of erythrohydroxybupropion in the humanbeing, on day 8, that is at least about 30 ng/mL, at least about 60ng/mL, at least about 90 ng/mL, at least about 100 ng/mL, at least about150 ng/mL, at least about 200 ng/mL, at least about 300 ng/mL, up toabout 1,000 ng/mL, or any C_(max) in a range bounded by, or between, anyof these values.

In some embodiments, bupropion, erythrohydroxybupropion, or a prodrug oferythrohydroxybupropion, may be administered to a human being in anamount that results in a C_(avg) of erythrohydroxybupropion in the humanbeing, on day 8, that is at least about 20 ng/mL, at least about 30ng/mL, at least about 50 ng/mL, at least about 80 ng/mL, at least about90 ng/mL, at least about 100 ng/mL, at least about 150 ng/mL, at leastabout 200 ng/mL, at least about 300 ng/mL, up to about 1,000 ng/mL, upto about 5,000 ng/mL, or any C_(avg) in a range bounded by, or between,any of these values.

For compositions comprising both dextromethorphan and bupropion, someliquids may comprise about 0.0001% (w/v) to about 50% (w/v), about 0.01%(w/v) to about 20% (w/v), about 0.01% to about 10% (w/v), about 1% (w/v)to about 3% (w/v), about 3% (w/v) to about 5% (w/v), about 5% (w/v) toabout 7% (w/v), about 5% (w/v) to about 15% (w/v), about 7% (w/v) toabout 10% (w/v), about 10% (w/v) to about 15% (w/v), about 15% (w/v) toabout 20% (w/v), about 20% (w/v) to about 30% (w/v), about 30% (w/v) toabout 40% (w/v), about 40% (w/v) to about 50% (w/v) of dextromethorphanand bupropion combined, or any amount in a range bounded by, or between,any of these values.

Some solid compositions may comprise at least about 5% (w/w), at leastabout 10% (w/w), at least about 20% (w/w), at least about 50% (w/w), atleast about 70% (w/w), at least about 80%, about 10% (w/w) to about 30%(w/w), about 10% (w/w) to about 20% (w/w), about 20% (w/w) to about 30%(w/w), about 30% (w/w) to about 50% (w/w), about 30% (w/w) to about 40%(w/w), about 40% (w/w) to about 50% (w/w), about 50% (w/w) to about 80%(w/w), about 50% (w/w) to about 60% (w/w), about 70% (w/w) to about 80%(w/w), about 80% (w/w) to about 90% (w/w) of dextromethorphan andbupropion combined, or any amount in a range bounded by, or between, anyof these values.

In some embodiments, the weight ratio of dextromethorphan to bupropionin a single composition or dosage form may be about 0.1 to about 2,about 0.2 to about 1, about 0.1 to about 0.3, about 0.2 to about 0.4,about 0.3 to about 0.5, about 0.5 to about 0.7, about 0.8 to about 1,about 0.2, about 0.3, about 0.4, about 0.45, about 0.6, about 0.9, orany ratio in a range bounded by, or between, any of these values.

A therapeutically effective amount of a therapeutic compound may varydepending upon the circumstances. For example, a daily dose ofdextromethorphan may in some instances range from about 0.1 mg to about1000 mg, about 40 mg to about 1000 mg, about 20 mg to about 600 mg,about 60 mg to about 700 mg, about 100 mg to about 400 mg, about 15 mgto about 20 mg, about 20 mg to about 25 mg, about 25 mg to about 30 mg,about 30 mg to about 35 mg, about 35 mg to about 40 mg, about 40 mg toabout 45 mg, about 45 mg to about 50 mg, about 50 mg to about 55 mg,about 55 mg to about 60 mg, about 20 mg to about 60 mg, about 60 mg toabout 100 mg, about 100 mg to about 200 mg, about 100 mg to about 140mg, about 160 mg to about 200 mg, about 200 mg to about 300 mg, about220 mg to about 260 mg, about 300 mg to about 400 mg, about 340 mg toabout 380 mg, about 400 mg to about 500 mg, about 500 mg to about 600mg, about 15 mg, about 30 mg, about 60 mg, about 120 mg, about 180 mg,about 240 mg, about 360 mg, or any daily dose in a range bounded by, orbetween, any of these values. Dextromethorphan may be administered oncedaily; or twice daily or every 12 hours, three times daily, four timesdaily, or six times daily in an amount that is about half, one third,one quarter, or one sixth, respectively, of the daily dose.

A daily dose of bupropion, may in some instances range from about 10 mgto about 1000 mg, about 50 mg to about 600 mg, about 100 mg to about2000 mg, about 50 mg to about 100 mg, about 70 mg to about 95 mg, about100 mg to about 200 mg, about 105 mg to about 200 mg, about 100 mg toabout 150 mg, about 150 mg to about 300 mg, about 150 mg to about 200mg, about 200 mg to about 250 mg, about 250 mg to about 300 mg, about200 mg about 300 mg, about 300 mg to about 400 mg, about 400 mg to about500 mg, about 400 mg to about 600 mg, about 360 mg to about 440 mg,about 560 mg to about 640 mg, or about 500 mg to about 600 mg, about 100mg, about 150 mg, about 200 mg, about 300 mg, about 400 mg, about 600mg, or any daily dose in a range bounded by, or between, any of thesevalues. Bupropion may be administered once daily; or twice daily orevery 12 hours, or three times daily in an amount that is about half orone third, respectively, of the daily dose.

In some embodiments: 1) about 50 mg/day to about 100 mg/day, about 100mg/day to about 150 mg/day, about 150 mg/day to about 300 mg/day, about150 mg/day to about 200 mg/day, about 200 mg/day to about 250 mg/day,about 250 mg/day to about 300 mg/day of bupropion, or about 300 mg/dayto about 500 mg/day of bupropion; and/or 2) about 15 mg/day to about 60mg/day, about 15 mg/day to about 30 mg/day, about 30 mg/day to about 45mg/day, about 45 mg/day to about 60 mg/day, about 60 mg/day to about 100mg/day, about 80 mg/day to about 110 mg/day, about 100 mg/day to about150 mg/day, or about 100 mg/day to about 300 mg/day of dextromethorphan,are administered to a human being in need thereof.

In some embodiments, about 150 mg/day of bupropion and about 30 mg/dayof dextromethorphan, about 150 mg/day of bupropion and about 60 mg/dayof dextromethorphan, about 150 mg/day of bupropion and about 90 mg/dayof dextromethorphan, about 150 mg/day of bupropion and about 120 mg/dayof dextromethorphan, about 200 mg/day of bupropion and about 30 mg/dayof dextromethorphan, about 200 mg/day of bupropion and about 60 mg/dayof dextromethorphan, about 200 mg/day of bupropion and about 90 mg/dayof dextromethorphan, about 200 mg/day of bupropion and about 120 mg/dayof dextromethorphan, about 300 mg/day of bupropion and about 30 mg/dayof dextromethorphan, about 300 mg/day of bupropion and about 60 mg/dayof dextromethorphan, about 300 mg/day of bupropion and about 90 mg/dayof dextromethorphan, or about 300 mg/day of bupropion and about 120mg/day of dextromethorphan is administered to the human being.

In some embodiments, about 100 mg/day of bupropion and about 15 mg/dayof dextromethorphan is administered to the human being for 1, 2, or 3days, followed by about 200 mg/day of bupropion and about 30 mg/day ofdextromethorphan. In some embodiments, about 100 mg/day of bupropion andabout 30 mg/day of dextromethorphan is administered to the human beingfor 1, 2, or 3 days, followed by about 200 mg/day of bupropion and about60 mg/day of dextromethorphan.

In some embodiments, about 75 mg/day of bupropion and about 15 mg/day ofdextromethorphan is administered to the human being for 1, 2, or 3 days,followed by about 150 mg/day of bupropion and about 30 mg/day ofdextromethorphan. In some embodiments, about 75 mg/day of bupropion andabout 30 mg/day of dextromethorphan is administered to the human beingfor 1, 2, or 3 days, followed by about 150 mg/day of bupropion and about60 mg/day of dextromethorphan.

An antidepressant compound, such as bupropion, may be administered foras long as needed to treat a neurological condition, such as pain,depression or cough. In some embodiments, an antidepressant compound,such as bupropion, and dextromethorphan are administered at least once aday, such as once daily or twice daily, for at least 1 day, at least 3days, at least 5 days, at least 7 days, at least 8 days, at least 9days, or at least 10 days, at least 14 days, at least 21 days, at least28 days, at least 30 days, at least 35 days, at least 42 days, at least60 days, at least 90 days, at least 180 days, at least 365 days, orlonger.

In some embodiments, co-administration of dextromethorphan withbupropion, hydroxybupropion, erythrohydroxybupropion,threohydroxybupropion, or a prodrug of any of these compounds, may occuronce a day for about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,or more days prior to co-administering dextromethorphan with bupropion,hydroxybupropion, erythrohydroxybupropion, threohydroxybupropion, or aprodrug of any of these compounds twice a day.

Therapeutic compounds may be formulated for oral administration, forexample, with an inert diluent or with an edible carrier, or it may beenclosed in hard or soft shell gelatin capsules, compressed intotablets, or incorporated directly with the food of the diet. For oraltherapeutic administration, the active compound may be incorporated withan excipient and used in the form of ingestible tablets, buccal tablets,troches, capsules, elixirs, suspensions, syrups, wafers, and the like.

Tablets, troches, pills, capsules and the like may also contain one ormore of the following: a binder such as gum tragacanth, acacia, cornstarch, or gelatin; an excipient, such as dicalcium phosphate; adisintegrating agent such as corn starch, potato starch, alginic acid,and the like; a lubricant such as magnesium stearate; a sweetening agentsuch as sucrose, lactose, or saccharin; or a flavoring agent such aspeppermint, oil of wintergreen, or cherry flavoring. When the dosageunit form is a capsule, it may contain, in addition to materials of theabove type, a liquid carrier. Various other materials may be present asa coating, for example, tablets, pills, or capsules may be coated withshellac, sugar or both. A syrup or elixir may contain the activecompound, sucrose as a sweetening agent, methyl and propylparabens aspreservatives, a dye and flavoring, such as cherry or orange flavor. Itmay be desirable for material in a dosage form or pharmaceuticalcomposition to be pharmaceutically pure and substantially nontoxic inthe amounts employed.

Some compositions or dosage forms may be a liquid or may comprise asolid phase dispersed in a liquid.

Therapeutic compounds may be formulated for parental or intraperitonealadministration. Solutions of the active compounds as free bases orpharmacologically acceptable salts can be prepared in water suitablymixed with a surfactant, such as hydroxypropylcellulose. A dispersioncan also have an oil dispersed within, or dispersed in, glycerol, liquidpolyethylene glycols, and mixtures thereof. Under ordinary conditions ofstorage and use, these preparations may contain a preservative toprevent the growth of microorganisms.

In some embodiments, the human being or the patient is, or is selectedfor being, Black or African American.

In some embodiments, the human being or the patient is, or is selectedfor being, white.

In some embodiments, the human being or the patient is, or is selectedfor being, Asian.

In some embodiments, the human being or the patient is, or is selectedfor being, Native Hawaiian or other Pacific Islander.

In some embodiments, the human being or the patient is, or is selectedfor being, Hispanic or Latino.

In some embodiments, the human being or the patient is, or is selectedfor being, Native American or Alaska Native.

In some embodiments, the human being or the patient is not, or isselected for not being, Hispanic or Latino.

SPECIFICALLY CONTEMPLATED EMBODIMENTS

The following are examples of embodiments that are specificallycontemplated by the inventor:

Embodiment 1. A method of treating pain or a neurological disordercomprising delivering an enhanced plasma level or bioavailability ofdextromethorphan or administering a therapeutically effective amount ofa combination of dextromethorphan and an antidepressant compound, to aperson in need thereof.Embodiment 2. A method of treating pain comprising administering acombination of an antidepressant compound and dextromethorphan to ahuman being in need thereof.Embodiment 3. A method of enhancing the pain relieving properties ofdextromethorphan, comprising co-administering dextromethorphan and anantidepressant compound.Embodiment 4. A method of increasing dextromethorphan plasma levels in ahuman being that is an extensive metabolizer of dextromethorphan,comprising co-administering an antidepressant compound to the humanbeing receiving a treatment that includes administration ofdextromethorphan.Embodiment 5. A method of inhibiting the metabolism of dextromethorphan,comprising administering an antidepressant compound to a human being,wherein the human being is an extensive metabolizer of dextromethorphan,and wherein dextromethorphan is present in the body of the human beingat the same time as the antidepressant compound.Embodiment 6. A method of increasing the metabolic lifetime ofdextromethorphan, comprising administering an antidepressant compound toa human being, wherein the human being is an extensive metabolizer ofdextromethorphan, and wherein dextromethorphan is present in the body ofthe human being at the same time as the antidepressant compound.Embodiment 7. A method of correcting extensive metabolism ofdextromethorphan, comprising administering an antidepressant compound toa human being in need thereof.Embodiment 8. A method of improving pain relieving properties ofdextromethorphan comprising administering an antidepressant compound inconjunction with administration of dextromethorphan to a human being inneed of treatment for pain.Embodiment 9. A method of improving antitussive properties ofdextromethorphan comprising administering an antidepressant compound inconjunction with administration of dextromethorphan to a human being inneed of treatment for cough.Embodiment 10. A method of treating cough comprising administering acombination of an antidepressant compound and dextromethorphan to ahuman being in need thereof.Embodiment 11. A method of improving a therapeutic property ofdextromethorphan comprising administering an antidepressant compound inconjunction with administration of dextromethorphan to a human being inneed of treatment for a neurological disorder.Embodiment 12. A method of treating a neurological disorder comprisingadministering a combination of an antidepressant compound anddextromethorphan to a human being in need thereof.Embodiment 13. A method of treating a neurological disorder comprisingadministering an antidepressant compound and dextromethorphan to a humanbeing in need thereof, wherein the human being is an extensivemetabolizer of dextromethorphan.Embodiment 14. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein thedextromethorphan and the antidepressant compound are administered inseparate dosage forms.Embodiment 15. A pharmaceutical composition comprising a therapeuticallyeffective amount of dextromethorphan, a therapeutically effective amountof an antidepressant compound, and a pharmaceutically acceptableexcipient.Embodiment 16. An oral dosage form comprising at least 20 mg ofdextromethorphan and an effective amount of an antidepressant compoundto inhibit the metabolism of dextromethorphan in a human being that isan extensive metabolizer of dextromethorphan.Embodiment 17. The oral dosage form of embodiment 16, wherein about 30mg to about 350 mg of dextromethorphan is present in the dosage form.Embodiment 18. The oral dosage form of embodiment 16 or 17, whereinabout 100 mg to about 400 mg of bupropion is present in the dosage form.Embodiment 19. The oral dosage form of any of embodiments 16, 17, or 18,comprising an amount of bupropion that results in a bupropion plasmalevel of about 0.1 μM to about 10 μM when the oral dosage form isadministered to a human being.Embodiment 20. The oral dosage form of embodiment 19, comprising anamount of bupropion that results in a bupropion plasma level of about0.1 μM to about 2 μM when the oral dosage form is administered to ahuman being.Embodiment 21. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, whereinbupropion is administered at a dose that results in a bupropion plasmalevel of about 0.1 μM to about 10 μM.Embodiment 22. The method of any preceding embodiment, such asembodiment 21, wherein bupropion is administered at a dose that resultsin a bupropion plasma level of about 0.3 μM to about 1 μM.Embodiment 23. The method, composition, or dosage form of any precedingembodiment, such as embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, or 17, wherein the antidepressant compound is bupropionor a metabolite thereof.Embodiment 24. The method, composition, or dosage form of any precedingembodiment, such as embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, or 17, wherein the antidepressant compound is bupropion.Embodiment 25. The method, composition, or dosage form of any precedingembodiment, such as embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, or 17, wherein the antidepressant compound isclomipramine, doxepin, fluoxetine, mianserin, imipramine,2-chloroimipramine, amitriptyline, amoxapine, desipramine,protriptyline, trimipramine, nortriptyline, maprotiline, phenelzine,isocarboxazid, tranylcypromine, paroxetine, trazodone, citalopram,sertraline, aryloxy indanamine, benactyzine, escitalopram, fluvoxamine,venlafaxine, desvenlafaxine, duloxetine, mirtazapine, nefazodone,selegiline, ketamine, or a pharmaceutically acceptable salt thereofEmbodiment 26. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 14, 21, 22, 23, 24, or25, wherein dextromethorphan is administered to the human being for thetreatment of cough.Embodiment 27. A method of treating a neurological disorder comprisingadministering about 150 mg/day to about 300 mg/day of bupropion andabout 30 mg/day to about 120 mg/day of dextromethorphan to a human beingin need thereof.Embodiment 28. A method of treating a neurological disorder comprisingadministering bupropion and dextromethorphan to a human being in needthereof, wherein the bupropion and dextromethorphan are administered atleast once a day for at least 8 days, at least 9 days, or at least 10days.Embodiment 29. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, or 27, wherein bupropion is administered to the human beingat least daily for at least 8 days, at least 9 days, or at least 10days.Embodiment 30. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, or 28, wherein dextromethorphan is administered to thehuman being at least daily for at least 8 days, at least 9 days, or atleast 10 days.Embodiment 31. The method of any preceding embodiment, such asembodiment 28, 29, or 30, wherein bupropion is administered in an amountthat results in a plasma concentration of dextromethorphan in the humanbeing, on day 8, that is at least 10 times the plasma concentration ofthe same amount of dextromethorphan administered without bupropion.Embodiment 32. The method of any preceding embodiment, such asembodiment 28, 29, 30, or 31, wherein bupropion is administered in anamount that results in an AUC₀₋₁₂ of hydroxybupropion, on day 8, that isat least about 3000 ng·hr/mL.Embodiment 33. The method of any preceding embodiment, such asembodiment 28, 29, 30, 31, or 32, wherein bupropion is administered inan amount that results in an AUC₀₋₁₂ of erythrohydroxybupropion, on day8, that is at least about 400 ng·hr/mL.Embodiment 34. The method of any preceding embodiment, such asembodiment 28, 29, 30, 31, 32, or 33, wherein bupropion is administeredin an amount that results in an AUC₀₋₁₂ of threohydroxybupropion, on day8, that is at least about 2000 ng·hr/mL.Embodiment 35. The method, composition, or dosage form of any precedingembodiment, such as embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31,32, 33, or 34, wherein the weight ratio of dextromethorphan to bupropionis about 0.1 to about 0.5.Embodiment 36. The method of any preceding embodiment, such asembodiment 27, 28, 29, 30, 31, 32, 33, 34, or 35, wherein the humanbeing is an extensive metabolizer of dextromethorphan.Embodiment 37. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, wherein about 150mg/day of bupropion and about 30 mg/day of dextromethorphan isadministered to the human being.Embodiment 38. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, wherein about 150mg/day of bupropion and about 60 mg/day of dextromethorphan isadministered to the human being.Embodiment 39. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, wherein about 200mg/day of bupropion and about 30 mg/day of dextromethorphan isadministered to the human being.Embodiment 40. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, wherein about 100mg/day of bupropion and about 15 mg/day of dextromethorphan isadministered to the human being for about 1 to about 3 days, followed byabout 200 mg/day of bupropion and about 30 mg/day of dextromethorphan.Embodiment 41. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, wherein about 200mg/day of bupropion and about 60 mg/day of dextromethorphan isadministered to the human being.Embodiment 42. The method of any preceding embodiment, such asembodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36, wherein about 100mg/day of bupropion and about 30 mg/day of dextromethorphan isadministered to the human being for about 1 to about 3 days, followed byabout 200 mg/day of bupropion and about 60 mg/day of dextromethorphan.Embodiment 43. The method of any preceding embodiment, such asembodiment 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 21, 22, 23, 24, 25, 26,27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, or 42,wherein dextromethorphan is administered to the human being for thetreatment of pain.Embodiment 44. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises postoperative pain, cancerpain, arthritic pain, lumbosacral pain, musculoskeletal pain, centralmultiple sclerosis pain, nociceptive pain, or neuropathic pain.Embodiment 45. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises musculoskeletal pain,neuropathic pain, cancer-related pain, acute pain, or nociceptive pain.Embodiment 46. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises postoperative pain.Embodiment 47. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises cancer pain.Embodiment 48. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises arthritic pain.Embodiment 49. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises lumbosacral pain.Embodiment 50. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises musculoskeletal pain.Embodiment 51. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises neuropathic pain.Embodiment 52. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises nociceptive pain.Embodiment 53. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises chronic musculoskeletal pain.Embodiment 54. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with rheumatoid arthritis.Embodiment 55. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with juvenile rheumatoidarthritis.Embodiment 56. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with osteoarthritis.Embodiment 57. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with an axialspondyloarthritis.Embodiment 58. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with ankylosingspondylitis.Embodiment 59. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with diabetic peripheralneuropathy.Embodiment 60. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with post-herpeticneuralgia.Embodiment 61. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with trigeminal neuralgia.Embodiment 62. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with monoradiculopathies.Embodiment 63. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with phantom limb pain.Embodiment 64. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with central pain.Embodiment 65. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises cancer-related pain.Embodiment 66. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with lumbar nerve rootcompression.Embodiment 67. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with spinal cord injury.Embodiment 68. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with post-stroke pain.Embodiment 69. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with central multiplesclerosis pain.Embodiment 70. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with HIV-associatedneuropathy.Embodiment 71. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with radio-therapyassociated neuropathy.Embodiment 72. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with chemo-therapyassociated neuropathy.Embodiment 73. The method of any preceding embodiment, such asembodiment 43, wherein the pain comprises dental pain.Embodiment 74. The method of any preceding embodiment, such asembodiment 43, wherein the pain is associated with primary dysmenorrhea.Embodiment 75. The method of any preceding embodiment, such asembodiment 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 21, 22, 23, 24, 25, 26,27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, or 74, wherein 90 mg/day ofdextromethorphan is administered to the human being.Embodiment 76. The method of any preceding embodiment, such asembodiment 75, wherein 45 mg of dextromethorphan is administered twice aday to the human being.Embodiment 77. The method of any preceding embodiment, such asembodiment 75 or 76, wherein 150 mg/day of bupropion is administered tothe human being.Embodiment 78. The method of any preceding embodiment, such asembodiment 75 or 76, wherein 180 mg/day of bupropion is administered tothe human being.Embodiment 79. The method of any preceding embodiment, such asembodiment 75 or 76, wherein 200 mg/day of bupropion is administered tothe human being.Embodiment 80. The method of any preceding embodiment, such asembodiment 75 or 76, wherein 300 mg/day of bupropion is administered tothe human being.Embodiment 81. A method of increasing dextromethorphan plasma levels ina human being, comprising co-administering threohydroxybupropion,hydroxybupropion, erythrohydroxybupropion, bupropion, or a prodrugthereof, with dextromethorphan to the human being, wherein thethreohydroxybupropion, hydroxybupropion, erythrohydroxybupropion,bupropion, or a prodrug thereof, is administered in an amount thatresults in an AUC₀₋₁₂ of dextromethorphan that is at least about 40ng·hr/mL.Embodiment 82. The method of any preceding embodiment, such asembodiment 81, wherein the AUC₀₋₁₂ of dextromethorphan is at least about50 ng·hr/mL.Embodiment 83. The method of any preceding embodiment, such asembodiment 81 or 82, wherein the human being is in need of treatmentwith dextromethorphan.Embodiment 84. The method of any preceding embodiment, such asembodiment 81, 82, or 83, wherein the human being is an extensivemetabolizer of dextromethorphan.Embodiment 85. The method of any preceding embodiment, such asembodiment 81, 82, 83, or 84, wherein the threohydroxybupropion,hydroxybupropion, erythrohydroxybupropion, bupropion, or a prodrugthereof, and dextromethorphan are administered to the human being atleast daily for at least 8 days, at least 9 days, or at least 10 days.Embodiment 86. The method of any preceding embodiment, such asembodiment 85, wherein the AUC₀₋₁₂ of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 100 ng·hr/mL.Embodiment 87. The method of any preceding embodiment, such asembodiment 85 or 86, wherein the AUC₀₋₁₂ of dextromethorphan on Day 8,Day 9, or Day 10 is at least about 400 ng·hr/mL.Embodiment 88. The method of any preceding embodiment, such asembodiment 85, 86, or 87, wherein the AUC₀₋₁₂ of dextromethorphan on Day8, Day 9, or Day 10 is at least about 800 ng·hr/mL.Embodiment 89. The method of any preceding embodiment, such asembodiment 85, 86, 87, or 88, wherein the AUC₀₋₁₂ of dextromethorphan onDay 8, Day 9, or Day 10 is at least about 1500 ng·hr/mL.Embodiment 90. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, or 89, wherein the AUC₀₋₂₄ ofdextromethorphan on Day 8, Day 9, or Day 10 is at least about 100ng·hr/mL.Embodiment 91. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, 89, or 90, wherein the AUC₀₋₂₄ ofdextromethorphan on Day 8, Day 9, or Day 10 is at least about 1500ng·hr/mL.Embodiment 92. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, 89, 90, or 91, wherein the AUC₀₋₂₄ ofdextromethorphan on Day 8, Day 9, or Day 10 is at least about 2900ng·hr/mL.Embodiment 93. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, 89, 90, 91, or 92, wherein the AUC_(0-inf) ofdextromethorphan on Day 8, Day 9, or Day 10 is at least about 100ng·hr/mL.Embodiment 94. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, 89, 90, 91, 92, or 93, wherein theAUC_(0-inf) of dextromethorphan on Day 8, Day 9, or Day 10 is at leastabout 1500 ng·hr/mL.Embodiment 95. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, 89, 90, 91, 92, 93, or 94, wherein theAUC_(0-inf) of dextromethorphan on Day 8, Day 9, or Day 10 is at leastabout 3500 ng·hr/mL.Embodiment 96. The method of any preceding embodiment, such asembodiment 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, or 95, wherein theAUC_(0-inf) of dextromethorphan on Day 8, Day 9, or Day 10 is at leastabout 5000 ng·hr/mL.Embodiment 97. A method of increasing dextromethorphan plasma levels ina human being, comprising co-administering threohydroxybupropion,hydroxybupropion, erythrohydroxybupropion, bupropion, or a prodrugthereof, with dextromethorphan to the human being, wherein thethreohydroxybupropion, hydroxybupropion, erythrohydroxybupropion,bupropion, or a prodrug thereof, is administered in an amount thatresults in a C_(max) of dextromethorphan that is at least about 6 ng/mL.Embodiment 98. The method of any preceding embodiment, such asembodiment 97, wherein the human being is in need of treatment withdextromethorphan.Embodiment 99. The method of any preceding embodiment, such asembodiment 97 or 98, wherein the human being is an extensive metabolizerof dextromethorphan.Embodiment 100. The method of any preceding embodiment, such asembodiment 97, 98, or 99, wherein the threohydroxybupropion,hydroxybupropion, erythrohydroxybupropion, bupropion, or a prodrugthereof, and dextromethorphan are administered to the human being atleast daily for at least 8 days, at least 9 days, or at least 10 days.Embodiment 101. The method of any preceding embodiment, such asembodiment 100, wherein the C_(max) of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 20 ng/mL.Embodiment 102. The method of any preceding embodiment, such asembodiment 100 or 101, wherein the C_(max) of dextromethorphan on Day 8,Day 9, or Day 10 is at least about 60 ng/mL.Embodiment 103. The method of any preceding embodiment, such asembodiment 100, 101, or 102, wherein the C_(max) of dextromethorphan onDay 8, Day 9, or Day 10 is at least about 120 ng/mL.Embodiment 104. A method of increasing dextromethorphan plasma levels ina human being, comprising co-administering threohydroxybupropion,hydroxybupropion, erythrohydroxybupropion, bupropion, or a prodrugthereof, with dextromethorphan to the human being, wherein thethreohydroxybupropion, hydroxybupropion, erythrohydroxybupropion,bupropion, or a prodrug thereof, is administered in an amount thatresults in a C_(avg) of dextromethorphan over a 12 hour period, afterone administration, that is at least about 5 ng/mL.Embodiment 105. The method of any preceding embodiment, such asembodiment 104, wherein the human being is in need of treatment withdextromethorphan.Embodiment 106. The method of any preceding embodiment, such asembodiment 104 or 105, wherein the human being is an extensivemetabolizer of dextromethorphan.Embodiment 107. The method of any preceding embodiment, such asembodiment 104, 105, or 106, wherein the threohydroxybupropion,hydroxybupropion, erythrohydroxybupropion, bupropion, or a prodrugthereof, and dextromethorphan are administered to the human being atleast daily for at least 8 days, at least 9 days, or at least 10 days.Embodiment 108. The method of any preceding embodiment, such asembodiment 107, wherein the C_(avg) of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 20 ng/mL.Embodiment 109. The method of any preceding embodiment, such asembodiment 107 or 108, wherein the C_(avg) of dextromethorphan on Day 8,Day 9, or Day 10 is at least about 70 ng/mL.Embodiment 110. The method of any preceding embodiment, such asembodiment 107, 108, or 109, wherein the C_(avg) of dextromethorphan onDay 8, Day 9, or Day 10 is at least about 120 ng/mL.Embodiment 111. A method of increasing dextromethorphan plasma levels ina human being, comprising co-administering bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a prodrug of any ofthese compounds, with dextromethorphan to the human being, wherein thebupropion or a prodrug thereof is administered in an amount that resultsin an AUC₀₋₁₂ of dextromethorphan that is at least about 40 ng·hr/mL.Embodiment 112. The method of any preceding embodiment, such asembodiment 111, wherein the AUC₀₋₁₂ of dextromethorphan is at leastabout 50 ng·hr/mL.Embodiment 113. The method of any preceding embodiment, such asembodiment 111 or 112, wherein the human being is in need of treatmentwith dextromethorphan.Embodiment 114. The method of any preceding embodiment, such asembodiment 111, 112, or 113, wherein the human being is an extensivemetabolizer of dextromethorphan.Embodiment 115. The method of any preceding embodiment, such asembodiment 111, 112, 113, or 114, wherein the bupropion or a prodrugthereof is co-administered with dextromethorphan at least daily for atleast two consecutive days.Embodiment 116. The method of any preceding embodiment, such asembodiment 115, wherein the bupropion or a prodrug thereof anddextromethorphan are administered to the human being at least daily forat least 8 days, at least 9 days, or at least 10 days.Embodiment 117. The method of any preceding embodiment, such asembodiment 116, wherein the AUC₀₋₁₂ of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 100 ng·hr/mL.Embodiment 118. The method of any preceding embodiment, such asembodiment 116, wherein the AUC₀₋₁₂ of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 800 ng·hr/mL.Embodiment 119. The method of any preceding embodiment, such asembodiment 116, wherein the AUC₀₋₁₂ of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 1500 ng·hr/mL.Embodiment 120. The method of any preceding embodiment, such asembodiment 116, wherein the AUC₀₋₂₄ of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 100 ng·hr/mL.Embodiment 121. The method of any preceding embodiment, such asembodiment 116, wherein the AUC₀₋₂₄ of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 1500 ng·hr/mL.Embodiment 122. The method of any preceding embodiment, such asembodiment 116, wherein the AUC_(0-inf) of dextromethorphan on Day 8,Day 9, or Day 10 is at least about 100 ng·hr/mL.Embodiment 123. The method of any preceding embodiment, such asembodiment 116, wherein the AUC_(0-inf) of dextromethorphan on Day 8,Day 9, or Day 10 is at least about 3500 ng·hr/mL.Embodiment 124. The method of any preceding embodiment, such asembodiment 116, wherein the AUC_(0-inf) of dextromethorphan on Day 8,Day 9, or Day 10 is at least about 5000 ng·hr/mL.Embodiment 125. A method of increasing dextromethorphan plasma levels ina human being, comprising co-administering bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a prodrug of any ofthese compounds, with dextromethorphan to the human being, wherein thebupropion or a prodrug thereof is administered in an amount that resultsin a C_(max) of dextromethorphan that is at least about 6 ng/mL.Embodiment 126. The method of any preceding embodiment, such asembodiment 125, wherein the human being is in need of treatment withdextromethorphan.Embodiment 127. The method of any preceding embodiment, such asembodiment 125 or 126, wherein the human being is an extensivemetabolizer of dextromethorphan.Embodiment 128. The method of any preceding embodiment, such asembodiment 126, 127, or 128, wherein the bupropion or a prodrug thereofis co-administered with dextromethorphan at least daily for at least twoconsecutive days.Embodiment 129. The method of any preceding embodiment, such asembodiment 128, wherein the bupropion or a prodrug thereof anddextromethorphan are administered to the human being at least daily forat least 8 days, at least 9 days, or at least 10 days.Embodiment 130. The method of any preceding embodiment, such asembodiment 129, wherein the C_(max) of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 10 ng/mL.Embodiment 131. The method of any preceding embodiment, such asembodiment 129, wherein the C_(max) of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 60 ng/mL.Embodiment 132. The method of any preceding embodiment, such asembodiment 129, wherein the C_(max) of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 120 ng/mL.Embodiment 133. A method of increasing dextromethorphan plasma levels ina human being, comprising co-administering bupropion, hydroxybupropion,erythrohydroxybupropion, threohydroxybupropion, or a prodrug of any ofthese compounds, with dextromethorphan to the human being, wherein thebupropion or a prodrug thereof is administered in an amount that resultsin a C_(avg) of dextromethorphan, over the period between two separateand consecutive administrations of dextromethorphan, that is at leastabout 5 ng/mL.Embodiment 134. The method of any preceding embodiment, such asembodiment 134, wherein the bupropion or a prodrug thereof isadministered in an amount that results in a C_(avg) of dextromethorphan,over the period between two separate and consecutive administrations ofdextromethorphan, that is at least about 60 ng/mL.Embodiment 135. The method of any preceding embodiment, such asembodiment 134, wherein the human being is in need of treatment withdextromethorphan.Embodiment 136. The method of any preceding embodiment, such asembodiment 134 or 135, wherein the human being is an extensivemetabolizer of dextromethorphan.Embodiment 137. The method of any preceding embodiment, such asembodiment 134, 135, or 136, wherein the bupropion or a prodrug thereofis co-administered with dextromethorphan at least daily for at least twoconsecutive days.Embodiment 138. The method of any preceding embodiment, such asembodiment 137, wherein the bupropion or a prodrug thereof anddextromethorphan are administered to the human being at least daily forat least 8 days, at least 9 days, or at least 10 days.Embodiment 139. The method of any preceding embodiment, such asembodiment 138, wherein the C_(avg) of dextromethorphan on Day 8, Day 9,or Day 10 is at least about 8 ng/mL, wherein the C_(avg) is for theperiod between two separate and consecutive administrations ofdextromethorphan, or if dextromethorphan is administered only once onDay 8, Day 9, or Day 10, the C_(avg) is for 12 hours after the firstdose of dextromethorphan on Day 8, Day 9, or Day 10.Embodiment 140. The method of any preceding embodiment, such asembodiment 138, wherein the Cavg of dextromethorphan on Day 8, Day 9, orDay 10 is at least about 120 ng/mL, wherein the C_(avg) is for theperiod between two separate and consecutive administrations ofdextromethorphan, or if dextromethorphan is administered only once onDay 8, Day 9, or Day 10, the C_(avg) for 12 hours after the first doseof dextromethorphan on Day 8, Day 9, or Day 10.Embodiment 141. A method of improving the efficacy of bupropion intreating depression, comprising: orally administering about 90 mg toabout 125 mg of a bupropion in combination with about 0.3 mg/kg to about1 mg/kg of a dextromethorphan, once or twice a day for at least 23 days,to a human being suffering from depression, wherein orally administeringthe bupropion in combination with the dextromethorphan is more effectivein treating depression than orally administering the same dosage regimenof bupropion without dextromethorphan.Embodiment 142. The method of embodiment 141, wherein about 0.6 mg/kg toabout 0.8 mg/kg of the dextromethorphan is orally administered once ortwice a day.Embodiment 143. The method of embodiment 141, wherein about 45 mg of thedextromethorphan is orally administered once or twice a day.Embodiment 144. The method of embodiment 141, wherein about 100 mg toabout 120 mg of the bupropion is orally administered once or twice aday.Embodiment 145. The method of embodiment 142, wherein about 105 mg ofthe bupropion is orally administered once or twice a day.Embodiment 146. The method of embodiment 141, wherein thedextromethorphan and the bupropion are orally administered for at least35 days.Embodiment 147. The method of embodiment 141, wherein the human being issuffering from treatment-resistant depression.Embodiment 148. The method of embodiment 141, wherein thedextromethorphan is orally administered in a dosage form that providesimmediate release of the dextromethorphan.Embodiment 149. The method of embodiment 143, wherein thedextromethorphan is orally administered in a dosage form that providesimmediate release of the dextromethorphan.Embodiment 150. The method of embodiment 141, wherein the bupropion isorally administered in a dosage form that provides sustained release ofthe bupropion.Embodiment 151. The method of embodiment 145, wherein the bupropion isorally administered in a dosage form that provides sustained release ofthe bupropion.Embodiment 152. The method of embodiment 150, wherein about 105 mg ofthe bupropion is orally administered once or twice a day in a dosageform that provides sustained release of the bupropion.Embodiment 153. The method of embodiment 152, wherein the bupropion andthe dextromethorphan are orally administered together in a single dosageform that is orally administered once or twice a day.Embodiment 154. The method of embodiment 153, wherein thedextromethorphan and the bupropion are orally administered for at least5 weeks.Embodiment 155. The method of embodiment 141, wherein the human being issuffering from major depressive disorder.Embodiment 156. The method of embodiment 154, wherein the bupropioncomprises an enantiomeric excess of an R-enantiomer.Embodiment 157. The method of embodiment 154, wherein the bupropioncomprises an enantiomeric excess of an S-enantiomer.Embodiment 158. The method of embodiment 141, wherein thedextromethorphan comprises a deuterium-modified dextromethorphan.Embodiment 159. The method of embodiment 141, wherein the human being iscurrently suffering from depression and has previously beenunsuccessfully treated with at least two antidepressants.Embodiment 160. A method of treating treatment-resistant depressioncomprising:

selecting a human being suffering from depression who has previouslybeen unsuccessfully treated with at least one antidepressant; and

orally administering a dextromethorphan-bupropion combination treatmentonce or twice a day to the human being for at least about five weeks;

wherein the dextromethorphan-bupropion combination treatment comprisesabout 40 mg to about 70 mg of a dextromethorphan and about 100 mg toabout 140 mg of a bupropion.

Embodiment 161. The method of embodiment 160, wherein the bupropioncomprises an enantiomeric excess of an enantiomer.

Embodiment 162. The method of embodiment 160, wherein thedextromethorphan comprises a deuterium-modified dextromethorphan.

Embodiment 163. The method of embodiment 160, wherein thedextromethorphan-bupropion combination treatment comprises about 40 mgto about 50 mg of the dextromethorphan.

Embodiment 164. The method of embodiment 160, wherein thedextromethorphan-bupropion combination treatment comprises about 100 mgto about 110 mg of the bupropion.

Embodiment 165. The method of embodiment 163, wherein thedextromethorphan-bupropion combination treatment comprises about 100 mgto about 110 mg of the bupropion.

Embodiment 166. The method of embodiment 165, wherein thedextromethorphan and the bupropion are orally administered in a singledosage form that provides immediate release for the dextromethorphan andsustained release for the bupropion.

Embodiment 167. The method of embodiment 166, further comprising orallyadministering the dextromethorphan-bupropion combination treatment oncea day for about 1, 2, 3, 4, 5, 6, or 7 days prior to orallyadministering the dextromethorphan-bupropion combination treatment twicea day to the human being for at least about five weeks.Embodiment 168. The method of embodiment 167, wherein thedextromethorphan-bupropion combination treatment comprises about 45 mgof the dextromethorphan.Embodiment 169. The method of embodiment 168, wherein thedextromethorphan-bupropion combination treatment comprises about 105 mgof the bupropion.Embodiment 170. The method of embodiment 160, wherein the antidepressantis duloxetine.Embodiment 171. A method of rapidly relieving the symptoms ofdepression, comprising administering a combination of bupropion anddextromethorphan once daily or twice daily to a human being in needthereof, wherein the human being experiences a therapeutic effect within2 weeks of the first day that the combination of bupropion anddextromethorphan is administered.Embodiment 172. A method of treating depression, comprisingadministering a combination of bupropion and dextromethorphan once dailyor twice daily to a human being in need thereof, wherein the human beingis of Asian descent.Embodiment 173. Use of a combination of bupropion and dextromethorphanin the manufacture of a medicament for rapidly relieving the symptoms ofdepression, wherein the medicament is administered once daily or twicedaily to achieve a therapeutic effect within 2 weeks of the first daythat the medicament is administered.Embodiment 174. Use of a combination of bupropion and dextromethorphanin the manufacture of a medicament for the treatment of a depression,wherein the medicament is administered once daily or twice daily to ahuman being of Asian descent.Embodiment 175. The method of embodiment 171 or 172 or the use ofembodiment 173 or 174, wherein the human being is of Japanese descent.Embodiment 176. The method of embodiment 171 or 172 or the use ofembodiment 173 or 174, wherein the human being is of Chinese descent.Embodiment 177. The method of embodiment 171 or 172 or the use ofembodiment 173 or 174, wherein the human being is of Korean descent.Embodiment 178. The method or the use of embodiment 171, 172, 173, 174,175, 176, or 177, wherein about 105 mg of bupropion hydrochloride, or amolar equivalent amount of: 1) another salt form of bupropion or a 2)free base form of bupropion, is orally administered once daily or twicedaily.Embodiment 179. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, or 178, wherein about 44 mg to about 46 mg ofdextromethorphan hydrobromide, or a molar equivalent amount of: 1)another salt form of dextromethorphan or a 2) free base form ofdextromethorphan, is orally administered once daily or twice daily.Embodiment 180. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, or 179, wherein the human being has previously hadan inadequate response to at least one antidepressant therapy.Embodiment 181. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, 179, or 180, wherein the depression is majordepressive disorder.Embodiment 182. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, 179, 180, or 181, wherein the depression istreatment resistant depression.Embodiment 183. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, 179, 180, 181, or 182, wherein the combination ofbupropion and dextromethorphan is administered once daily or twice dailyfor at least 30 days.Embodiment 184. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, 179, 180, 181, or 182, wherein the combination ofbupropion and dextromethorphan is administered once daily or twice dailyfor at least 42 days.Embodiment 185. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, 179, 180, 181, 182, 183, or 184, whereinadministration of the combination of bupropion and dextromethorphanresults in the MADRS score reduced by at least about 10% as comparedwith baseline.Embodiment 186. The method or the use of embodiment 171, 172, 173, 174,175, 176, 177, 178, 179, 180, 181, 182, 183, or 184, whereinadministration of the combination of bupropion and dextromethorphanresults in the MADRS score reduced by at least about 10% as comparedwith placebo.Embodiment 187. A method of treating nicotine addiction associated withsmoking tobacco comprising administering a combination of a bupropionand a dextromethorphan daily for at least 21 consecutive days to aperson suffering from nicotine addiction, wherein the person is anad-lib tobacco smoker, wherein a total amount of 200 mg to 250 mg ofbupropion and 80 mg to 140 mg of dextromethorphan are administered tothe person daily, and wherein the method is more effective thanadministering the same amount of bupropion alone.Embodiment 188. The method of embodiment 187, wherein the administrationof the combination of the bupropion and the dextromethorphan resulted inat least 10% greater reduction in an intensity of the nicotineself-administration as compared to bupropion alone as measured by thereduction in the average number of cigarettes smoked per day.Embodiment 189. The method of embodiment 187, wherein the administrationof the combination of the bupropion and the dextromethorphan resulted inat least 15% greater reduction in an intensity of the nicotineself-administration as compared to bupropion alone as measured by thereduction in the average number of cigarettes smoked per day.Embodiment 190. The method of embodiment 187, wherein the administrationof the combination of the bupropion and the dextromethorphan resulted inat least 20% greater reduction in an intensity of the nicotineself-administration as compared to bupropion alone as measured by thereduction in the average number of cigarettes smoked per day.Embodiment 191. The method of embodiment 187, wherein the administrationof the combination of the bupropion and the dextromethorphan resulted inat least 10% greater reduction in expired carbon monoxide levels ascompared to bupropion alone.The method of embodiment 1, wherein the person taking a medication ofthe combination of the bupropion and the dextromethorphan twice a day in2 equal amount of divided doses resulted in greater reduction in anintensity of the nicotine self-administration on the day or followingday of the administration than the person taking only one of the 2divided doses or not taking the medication of the combination.Embodiment 192. The method of embodiment 187, wherein the combination ofthe bupropion and the dextromethorphan is administered to the persondaily for at least 42 consecutive days.Embodiment 193. The method of embodiment 187, wherein about 105 mg ofthe bupropion is administered to the person twice daily.Embodiment 194. The method of embodiment 187, wherein about 200 mg toabout 250 mg of the bupropion is administered daily to the person in twodivided doses.Embodiment 195. The method of embodiment 187, wherein about 90 mg of thedextromethorphan is administered to the person daily.Embodiment 196. The method of embodiment 187, wherein about 45 mg of thedextromethorphan in each dose is administered to the person twice daily.Embodiment 197. The method of embodiment 1, wherein about 40 mg to about50 mg of the dextromethorphan in each dose is administered to the persontwice daily.Embodiment 198. The method of embodiment 187, wherein about 45 mg of thedextromethorphan and about 105 mg of bupropion are administered to theperson twice daily.Embodiment 199. The method of embodiment 187, wherein the weight ratioof dextromethorphan to bupropion is about 0.1 to about 0.5.Embodiment 200. The method of embodiment 187, wherein the weight ratioof dextromethorphan to bupropion is about 0.4 to about 0.5.Embodiment 201. The method of embodiment 187, wherein, to the personaddicted to nicotine, the method is more effective than administeringthe dextromethorphan alone.Embodiment 202. The method of embodiment 187, wherein about 105 mg ofthe bupropion is administered to the person once daily for three days,followed by administering 105 mg of the bupropion in each dose twicedaily to the person for at least 21 days.Embodiment 203. The method of embodiment 202, wherein, to the personaddicted to nicotine, the method is more effective, as measured on day24 of treatment, than a control method, wherein the control methodconsists of administering 105 mg of the bupropion alone to the persononce daily for three days, followed by administering 105 mg of thebupropion alone in each dose twice daily to the person for 21 days.Embodiment 204. The method of embodiment 187, wherein about 105 mg ofthe bupropion is administered to the person once daily for three days,followed by administering 105 mg of the bupropion in each dose twicedaily to the person for at least 39 days.Embodiment 205. The method of embodiment 204, wherein, to the personaddicted to nicotine, the method is more effective, as measured on day42 of treatment, than a control method, wherein the control methodconsists of administering 105 mg of the bupropion alone to the persononce daily for three days, followed by administering 105 mg of thebupropion alone in each dose twice daily to the person for 39 days.Embodiment 206. The method of embodiment 204, wherein, to the personaddicted to nicotine, the method is more effective, as measured on day42 of treatment, than a control method, wherein the control methodconsists of administering 105 mg of the bupropion alone to the persononce daily for three days, followed by administering 105 mg of thebupropion alone in each dose twice daily to the person for 39 days.Embodiment 207. The method of embodiment 187, wherein about 45 mg of thedextromethorphan is administered to the person once daily for threedays, followed by administering 45 mg of the dextromethorphan in eachdose twice daily to the person for at least 21 days.Embodiment 208. The method of embodiment 198, wherein the method is moreeffective, as measured on day 21 of treatment, than a control method,wherein the control method consists of administering 105 mg of thebupropion alone to the person twice daily to the person for 21 days.Embodiment 209. The method of embodiment 187, wherein the bupropion hasan enantiomeric excess of the R-enantiomer that is at least 90%.Embodiment 210. The method of embodiment 187, wherein the bupropion hasan enantiomeric excess of the S-enantiomer that is at least 90%.Embodiment 211. The method of embodiment 187, wherein the bupropion isdeuterium enriched.Embodiment 212. The method of embodiment 187, wherein thedextromethorphan is deuterium enriched.

EXAMPLES Example 1

Fifteen human subjects were randomized into one of two treatment groupsreceiving either dextromethorphan (DM) alone, or DM in combination withbupropion, as shown in Table 1 below.

TABLE 1 Study Design Dose Levels Total Group Bupropion/DM Dosing RegimenDuration Subjects A  0 mg/60 mg DM: Twice daily, Days 1-8 Days 1-8 8 B150 mg/60 mg Bupropion: Once Days 1-8 7 daily, Days 1-3; Twice daily,Days 4-8 DM: Twice daily, Days 1-8

All subjects were extensive, including ultra-rapid, metabolizers ofdextromethorphan as determined by CYP2D6 genetic testing.Dextromethorphan was dosed at 12-hour intervals on Days 1-8, with afinal morning dose on Day 8. Bupropion was dosed once daily on Days 1-3,and at 12-hour intervals thereafter, with a final morning dose on Day 8.

Plasma samples were collected for concentration analysis ofdextromethorphan, total dextrorphan, bupropion, hydroxybupropion,erythrohydroxybupropion, and threohydroxybupropion on days 1 and 8.Plasma samples for determination of trough concentrations ofdextromethorphan were obtained approximately 12 hours after dosing ondays 1, 5, 6, and 8.

Concentrations of dextromethorphan, total dextrorphan (unconjugated andglucuronide forms), bupropion, hydroxybupropion,erythrohydroxybupropion, and threohydroxybupropion, were determinedusing LC-MS/MS. Pharmacokinetic parameters were calculated.

Phenotypic determination of dextromethorphan metabolizer status wasperformed by calculating the dextromethorphan/dextrorphan metabolicratio as described in Jurica et al. Journal of Clinical Pharmacy andTherapeutics, 2012, 37, 486-490. Plasma concentrations ofdextromethorphan and dextrorphan 3 hours after dosing were used, with adextromethorphan/dextrorphan ratio of 0.3 or greater indicating a poormetabolizer phenotype.

Results

Plasma concentrations of dextromethorphan were significantly increasedwith bupropion administration, as illustrated in FIG. 1 and Table 2.

TABLE 2 Mean Day 8 Dextromethorphan Plasma Concentrations (ng/mL)Dextromethorphan + Time Dextromethorphan Bupropion (hours) (Group A)(Group B) 0 1.2 110.6 1 2.4 129.3 2 3.6 153.9 3 3.6 151.6 4 3.3 149.1 62.5 150.0 8 1.9 144.4 12 1.1 119.3 24 0.4 95.3 36 0.1 69.0

The AUG of dextromethorphan was significantly increased withadministration of bupropion as show in FIGS. 2-4. As shown in FIG. 5 andTable 2A, administration of bupropion with dextromethorphan resulted inan approximately 60-fold, 80-fold, and 175-fold increase in meandextromethorphan AUC₀₋₁₂, AUC₀₋₂₄, and AUC_(0-inf), respectively on Day8 as compared to administration of dextromethorphan alone. As shown inFIG. 6 and Table 2B, the increase in dextromethorphan AUG occurred asearly as Day 1 (an approximate 3-fold increase in AUC₀₋₁₂).

TABLE 2A Day 8 Values Dextro- Dextromethorphan + methorphan Bupropion(Group (Group A) B) AUC₀₋₁₂ (ng * hr/mL) 28.1 1,686.3 AUC₀₋₂₄ (ng *hr/mL) 37.1 2,975.3 AUC_(0-inf) (ng * hr/mL) 41.2 7,237.3 C_(max)(ng/mL) 3.8 158.1 C_(min) (ng/mL) 1.1 119.3 C_(avg) (ng/mL) 2.3 140.5

TABLE 2B Day 1 Values Dextro- Dextromethorphan + methorphan Bupropion(Group (Group A) B) AUC₀₋₁₂ (ng * hr/mL) 20.1 56.5 C_(max) (ng/mL) 3.08.7

Trough plasma concentrations (also referred to as “minimum mean plasmaconcentrations” or “C_(min)”) of dextromethorphan were significantlyincreased with administration of bupropion as illustrated in FIG. 7 andTables 2A and 3. Administration of bupropion with dextromethorphanresulted in an approximately 105-fold increase in mean trough plasmaconcentration of dextromethorphan on Day 8 as compared to administrationof dextromethorphan alone.

Mean average plasma concentrations (C_(avg)) of dextromethorphan on Day8 increased approximately 60-fold with bupropion administration ascompared to administration of dextromethorphan alone, as illustrated inTable 2A. Maximum mean plasma concentrations (C_(max)) were alsosignificantly increased as illustrated in FIG. 8 and Table 2A.

TABLE 3 Mean Trough Dextromethorphan Plasma Concentrations (ng/mL)Dextro- Dextromethorphan + methorphan Bupropion Fold (Group A) (Group B)Change Day 1 0.7 2.5 3.5 Day 5 1.2 80.9 70 Day 6 1.3 102.2 78 Day 7 1.2110.6 94 Day 8 1.1 119.3 105

The T_(max) and elimination half-life (T_(1/2 el)) of dextromethorphanwere significantly increased with administration of bupropion on Day 8.The increase of T_(1/2 el) shows that the metabolic lifetime ofdextromethorphan was increased. Administration of bupropion withdextromethorphan resulted in a mean T_(max) of 3.6 hours, compared to2.3 hours for dextromethorphan alone. Administration of bupropion withdextromethorphan resulted in a mean T_(1/2 el) of 27.7 hours, comparedto 6.6 hours for dextromethorphan alone.

Plasma concentrations of dextrorphan were significantly decreased withbupropion administration, as illustrated in FIG. 9 and Table 4.

TABLE 4 Mean Day 8 Dextrorphan Plasma Concentrations (ng/mL) Dextro-Dextromethorphan + Time methorphan Bupropion (hours) (Group A) (Group B)0 132.4 165.3 1 688.9 190.7 2 959.1 214.9 3 778.1 214.4 4 594.9 205.1 6324.7 172.5 8 189.6 159.6 12 74.8 152.8 24 12.2 133.0 36 0.1 107.6

As shown in FIGS. 10-11, there was an approximate 78% reduction in meandextrorphan C_(max), and an approximate 55% reduction in meandextrorphan AUC₀₋₁₂ on Day 8 with administration of bupropion.

Phenotypic determination of dextromethorphan metabolizer status showedthat no subjects in either treatment arm were poor metabolizers onDay 1. On Day 8 however, 100% of subjects treated with bupropion hadconverted to poor metabolizer status as compared to 0% of subjectstreated with dextromethorphan alone. The mean plasmadextromethorphan/dextrorphan metabolic ratio increased from 0.01 on Day1 to 0.71 on Day 8 with bupropion administration. The mean ratio in thegroup administered DM alone was 0.00 on Day 1 and remained unchanged onDay 8.

On Day 8, average plasma concentrations of bupropion, hydroxybupropion,erythrohydroxybupropion, and threohydroxybupropion were at least 10ng/mL, 200 ng/mL, 20 ng/mL, and 100 ng/mL, respectively after bupropionadministration.

As used in this section, the term “fold change” or “fold increase”refers to the ratio of a value for bupropion with dextromethorphan tothe same value for dextromethorphan alone (i.e. the value for bupropionwith dextromethorphan divided by the same value for dextromethorphanalone).

Example 2

The ability of various antidepressant compounds to inhibit themetabolism of dextromethorphan was examined using human livermicrosomes. Each antidepressant compound was incubated at sevenincreasing concentrations (0.1-100 μM) in duplicate with human livermicrosomes (0.5 mg/mL) in the presence of dextromethorphan (5 μM) at 37°C. The assay was performed in the presence of 2 mM NADPH in 100 mMpotassium phosphate (pH 7.4) containing 5 mM magnesium chloride, in a200 μL assay final volume.

After optimal incubation at 37° C., the reactions were terminated byaddition of methanol containing internal standard for analyticalquantification. The quenched samples were incubated at 4° C. for 10minutes and centrifuged at 4° C. for 10 minutes. The supernatant wasremoved and the metabolite of dextromethorphan (dextrorphan) wasanalyzed by LC-MS/MS. A decrease in the formation of the metabolitecompared to vehicle control was used to calculate an IC₅₀ value (thetest concentration which produces 50% inhibition of dextromethorphanmetabolism) for each antidepressant compound, with a lower IC₅₀indicating greater potency.

The results are summarized in Table 5 below, and the correspondingpotencies are depicted in FIG. 12.

TABLE 5 Potency of Various Antidepressant Compounds for Inhibition ofthe Metabolism of Dextromethorphan in Human Liver Microsomes TestCompound Mean IC₅₀ (μM) Desvenlafaxine 97.3 Venlafaxine 27.7Escitaloprann 17.1 Citalopram 14.1 (2S,3S)-Hydroxybupropion 12.5Bupropion 9.1 (R,R)-Hydroxybupropion 8.2 Fluvoxamine 6.5 Sertraline 5.1(S)-Duloxetine 4.1 Threohydroxybupropion 3.9 Erythrohydroxybupropion 1.4

Example 3

Phase 2 Clinical Trial Design:

The Phase 2 clinical trial with the administration of a combination ofdextromethorphan and bupropion (DM/BU) was a randomized, double-blind,active-controlled, multi-center, U.S. trial with 80 adult patients withconfirmed diagnosis of moderate to severe major depressive disorder(MDD), who received a twice daily dose for a 6-week treatment period.Dose groups (1:1 randomization) included DM/BU (45 mgdextromethorphan/105 mg bupropion) with 43 patients, or activecomparator bupropion (105 mg) with 37 patients. Among these patients,23% of them had received prior first line treatment for depression. Theclinical trial had extensive quality control measures.

The Primary Endpoint:

The changes from baseline in the Montgomery-Åsberg Depression RatingScale (MADRS) total score over the 6-week treatment period werecalculated at each time point and averaged.

FIG. 13 and Table A shows the changes in MADRS total score over the timeduring the 6-week dosing period for the subjects administered bupropion(BU) or the combination of dextromethorphan and bupropion (DM/BU).

TABLE A Primary Endpoint DM + BU BU P-Value Change in MADRS −13.7 −8.8<0.001 Total Score over 6-week period (averaged) Change in MADRS −17.2−12.1 0.013 Total Score at week 6The Secondary Endpoints:

Table B listed the secondary endpoints with P-values.

TABLE B Secondary Endpoint P-Value* MADRS Total Score Change Weeks 1-20.01 % Achieving Remission on MADRS at Week 2 0.004 % AchievingRemission on MADRS at Week 6 0.004 MADRS-6 Change at Week 6 0.007 % ofResponders on MADRS-6 0.014 (≥50% reduction from baseline) at Week 6Clinical Global Impression-Improvement 0.045 (CGI-I) at Week 1 CGI-I atWeek 6 0.051 Clinical Global Impression-Severity (CGI-S) at Week 6 0.028*P-values are for DM/BU versus active comparator bupropion (BU).Multiple secondary endpoints favored DM/BU.

FIG. 14 shows the percent of subjects achieving remission (as determinedby MADRS≤10) over the time during the 6-week dosing period for thesubjects administered bupropion (BU) or the combination ofdextromethorphan and bupropion (DM/BU).

Safety:

The clinical study showed that the administration of the DM/BU was safeand well tolerated with similar rates of adverse events in the DM/BU andbupropion arms. No serious adverse events were observed. There was nomeaningful difference between the two treatment arms in discontinuationsdue to adverse events. The most commonly reported adverse events in theDM/BU arm were nausea, dizziness, dry mouth, decreased appetite, andanxiety. The DM/BU was not associated with psychotomimetic effects,weight gain, or increased sexual dysfunction.

Summary:

Statistically significant improvements on MADRS and secondary efficacyendpoints for DM/BU in patients with MDD were achieved. Early andsustained separation from active comparator bupropion were observed. Theadministration of DM/BU was safe and well-tolerated with nopsychotomimetic effects, weight gain, or increased sexual dysfunction

Thus, DM/BU demonstrated significant and rapid antidepressant activitywith a favorable safety profile in the clinical trial in MDD.

Results:

FIGS. 13 and 14 are prepared based on the results of the US clinicaltrials with 80 adult patients having depression with 43 patients treatedwith the combination of 45 mg of DM and 105 mg of BU, and 37 patientstreated with 105 mg of BU alone who received a twice daily dose for the6-week treatment period. Among these patients, 23% of them had receivedprior first line treatment for depression.

As shown in FIG. 13 and Table A, the MADRS total score (depressionrating scale) was significantly reduced with the combination of DM andBU than that of BU alone even at the first week of the treatment. Atweek 6, administration of the combination DM/BU reduced the MADRS totalscore by about 42% as compared to bupropion alone.

As shown in FIG. 14, even in as early as the second week of thetreatment, the remission rate for the combination of DM/BU issignificantly higher than that for the comparator BU alone (about 8times) with about 20% higher remission rate. At week 6 of the treatment,the administration of combination DM/BU resulted in about 30% higherremission rate than that of the comparator BU alone.

The above clinical study showed that the administration of thecombination of bupropion with dextromethorphan (DM/BU) provides greaterefficacy than would otherwise be achieved by administering bupropionalone. This clinical study demonstrated that the combination ofdextromethorphan and bupropion has an additive or synergistic efficacyin treating depression.

Example 4: Product Kit

In some embodiments, a product kit comprises a combination ofdextromethorphan and bupropion, for treating depression, wherein theproduct kit contains a dosage form containing about 30 mg to about 60 mgof dextromethorphan and about 100 mg to about 200 mg of bupropion, andwherein administration of the dosage form once daily or twice dailyresults in greater efficacy in the human being than that foradministering bupropion alone. In some embodiments, the product kitcontains 45 mg of dextromethorphan and 105 mg of bupropion.

In some embodiments, a product kit comprises an oral sustained releasedelivery system for dextromethorphan, comprising bupropion;dextromethorphan; and a water soluble vehicle in a dosage form, whereinthe dosage form contains about 30 mg to about 60 mg of dextromethorphanand about 100 mg to about 200 mg of bupropion, and wherein the use ofthe dosage form once or twice daily for at least eight days results inthe increase of elimination half-life (T_(1/2)) of dextromethorphan thanthat for administration dextromethorphan alone on the eighth day.

Example 5

Nearly 40 million American adults smoke and around 70% of them reportthat they want to quit. Tobacco use results in approximately 500,000premature deaths each year in the U.S. alone, according to the Centersfor Disease Control and Prevention. Smoking is the single largest causeof premature deaths worldwide accounting for an estimated almost 20% ofall deaths in developed countries [Dani J A and Heinemann S (1996)Neuron 16:5, pp. 905-8]. Direct health care and lost productivity costsas a result of smoking total nearly $300 billion a year in the U.S.alone. It is estimated that only 3 to 5% of cigarette smokers whoattempt to quit without assistance are successful for 6-12 months, andthe relapse rate remains above 80% even with current treatments [HughesJ R, et al. (2004) Addiction 99:1, pp. 29-38]. As the vast majority ofsmokers who attempt to quit fail to do so highlighting the need for newapproaches. The combination of dextromethorphan and bupropion (DM/BU)has the potential to address this condition due to the novel mechanismsof action of DM/BU.

The dextromethorphan component of DM/BU is a sigma-1 receptor agonist,nicotinic acetylcholine receptor antagonist, and inhibitor of theserotonin and norepinephrine transporters. The bupropion component ofDM/BU serves to increase the bioavailability of dextromethorphan, and isa norepinephrine and dopamine reuptake inhibitor, and a nicotinicacetylcholine receptor antagonist. Both components of DM/BU arenicotinic acetylcholine receptor antagonists, a mechanism that isrelevant to nicotine dependence. Thus, DM/BU provides a potentially newmechanism of action for smoking cessation treatment.

Phase 2 Clinical Trial Design:

The clinical trial was a Phase 2, randomized, double-blind,active-controlled study to evaluate the efficacy and safety of DM/BU forsmoking cessation treatment. A total of 58 smokers were randomized in a1:1 ratio to receive either DM/BU (45 mg dextromethorphan/105 mgbupropion) (n=31), or the active comparator bupropion (105 mg) (n=27),twice daily, and assessed over a 3-week period. Enrolled subjects weredaily smokers using 10 or more cigarettes per day. The average number ofcigarettes smoked per day at baseline was 20 for DM/BU and 17 for thebupropion treatment groups.

The Primary Endpoint:

The primary outcome measure was the change in smoking intensity,measured using the number of cigarettes smoked per day, assessed viadaily smoking diaries.

Reduction in ad-lib smoking was selected as the primary endpoint in thistrial, because it has been shown to correlate with smoking abstinence.

Safety:

Medication adherence was similar between the study arms for both themorning dose (97.1% for DM/BU and 96.6% for bupropion) and the eveningdose (76.3% for DM/BU and 79.4% for bupropion). In the study, DM/BU wassafe and well tolerated with no serious adverse events. The mostcommonly reported side effects were headache, dry mouth, andinsomnia/vivid dreams, with similar incidences in both treatment arms.

Results:

Treatment with DM/BU resulted in a 25% greater reduction in the averagenumber of cigarettes smoked per day over the 3-week period, theprespecified primary endpoint, as compared to bupropion (averagereductions of 8.49 and 6.79 cigarettes per day for DM/BU and bupropion,respectively, p=0.0016).

Consistent with this finding, a greater proportion of smokers receivingDM/BU experienced a more than 50% reduction in expired carbon monoxidelevels, a biochemical marker of smoking intensity, as compared to thosetreated with bupropion (52.0% for DM/BU versus 30.4% for bupropion,p=0.15).

In addition, the human subjects who took DM/BU as prescribed on a givenday smoked 1.0 fewer cigarette on the day of medication use of DM/BU(p=0.026) and 1.2 fewer cigarettes on the following day (p=0.008) ascompared to those who missed one or both doses of DM/BU.

Summary:

The treatment with DM/BU achieves the prespecified primary endpoint inPhase 2 Trial in Smoking Cessation. The treatment with DM/BUdemonstrated statistically significant reduction in daily smokingcompared to the active comparator bupropion alone (p=0.0016). Thefindings in this phase 2 clinical trial are notable because DM/BU wascompared to bupropion, which is an approved treatment for smokingcessation.

Furthermore, it is worth noting that the improvement of DM/BU overbupropion observed in this clinical trial in human beings is similar inmagnitude to the improvement over placebo reported for the approvedsmoking cessation treatment varenicline in studies with a similardesign. Varenicline is a prescription medication used to treat smokingaddiction. This medication is the first approved nicotinic receptorpartial agonist. Specifically, varenicline is a partial agonist of thealpha4/beta2 subtype of the nicotinic acetylcholine receptor.

Example 6

A Phase 3, randomized, double-blind, multicenter, placebo-controlledclinical trial of the combination of dextromethorphan (DM) and bupropion(BU or BUP) in patients with major depressive disorder (MDD) wasconducted in the U.S. A total of 327 patients with a confirmed diagnosisof moderate to severe MDD were randomized in a 1:1 ratio to receive 45mg dextromethorphan/105 mg bupropion (DM/BU) (n=163), or placebo (n=164)once daily for the first 3 days (day 1, day 2, and day 3) and twicedaily thereafter (starting day 4) for a total of 6 weeks.

Baseline inclusion criteria included: Male or female 18-65 years of age,meeting DSM-5 criteria for current MDD without psychotic features, aMontgomery-Åsberg Depression Rating Scale (MADRS) total score of atleast 25, and CGI-S score of at least 4. Exclusion criteria included: ahistory of electroconvulsive therapy, vagus nerve stimulation,transcranial magnetic stimulation, or any experimental central nervoussystem treatment of, during the current episode or in the past 6 months,Schizophrenia, bipolar disorder, obsessive compulsive disorder, andPsychiatric symptoms secondary to any other general medical condition.

Patient demographics and baseline characteristics are shown in Table 6below:

TABLE 6 45 mg DM/ 105 mg BU Placebo Age (years) 42.1 (12.71) 41.1(13.78) Female Gender, n (%) 98 (60.1%) 117 (71.3%) Race, n (%) White 88(54.0%) 92 (56.1%) Black or African American 61 (37.4%) 55 (33.5%) Asian9 (5.5%) 8 (4.9%) Other or Not Reported 5 (3.1%) 9 (5.5%) BMI (mg/kg²)29.2 (5.59) 29.4 (5.66) MADRS Total Score 33.6 (4.43) 33.2 (4.36) CGI-SScore 4.6 (0.59) 4.6 (0.57) Data are mean (SD) unless otherwise stated.Abbreviations: BMI = Body Mass Index; BU = Bupropion; CGI-S = ClinicalGlobal Impression-Severity; DM = Dextromethorphan; MADRS =Montgomery-Asberg Depression Rating Scale

Demographics and baseline characteristics were similar across bothtreatment groups. Study completion rates were greater than 75% in bothtreatment groups.

The primary endpoint of the study was the change from baseline in theMADRS total score at Week 6. Secondary endpoints included MADRS changeat Weeks 1 and 2, remission, response, Clinical GlobalImpression-Improvement (CGI-I), Clinical Global Impression-Severity(CGI-S), Patient Global Impression-Improvement (PGI-I), MADRS-6, SheehanDisability Scale (SDS), other quality of life measures, safety andtolerability. P-values were calculated based on least square meanestimates.

DM/BU met the primary endpoint and rapidly and significantly improvedsymptoms of depression. Specifically, DM/BU demonstrated rapid, durable,and statistically significant improvement in depressive symptoms asmeasured by MADRS total score compared to placebo (p=0.002 on primaryendpoint). DM/BU demonstrated a highly statistically significantreduction in the Montgomery-Åsberg Depression Rating Scale (MADRS) totalscore compared to placebo at Week 6, with mean reductions from baselineof 16.6 points for DM/BU and 11.9 points for placebo (p=0.002).

Additionally, a statistically significant improvement was observed atWeek 1, or only 4 days after the start of twice daily dosing. Asdepicted in FIG. 15, statistically significant improvements at Week 1were observed for MADRS total score, with a reduction in MADRS totalscore of 7.3 points for DM/BU compared to the reduction of 4.9 pointsfor placebo (key secondary endpoint, p=0.007), with statisticalsignificance for this measure maintained at all time points thereafter(e.g. Week 2, 3, 4, 5, or 6). Statistically significant improvements forPatient Global Impression-Improvement (PGI-I) (p=0.008); Clinical GlobalImpression-Severity (CGI-S) (p=0.013); Clinical GlobalImpression-Improvement (CGI-I) (p=0.035); Quick Inventory of DepressiveSymptomatology-Self-Rated (QIDS-SR-16) (p=0.016); Quality of LifeEnjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF)(p=0.031); and other endpoints were also observed at Week 1 and at everytime point thereafter (e.g. Week 2, 3, 4, 5, or 6).

As shown in FIG. 16, response, defined as a 50% improvement in the MADRStotal score, was seen at Week 6 in 54.0% of patients who received DM/BU,compared to 34.0% of patients who received placebo (p<0.001).

As shown in FIG. 17, rates of remission from depression (defined asMADRS≤10) were statistically significantly greater for DM/BU compared toplacebo at Week 2 (p=0.013) and at every time point thereafter (e.g.Week 3, 4, or 6), being achieved by 39.5% of DM/BU patients compared to17.3% of placebo patients at Week 6 (p<0.001).

DM/BU was also associated with a statistically significant reduction infunctional impairment, as measured by the Sheehan Disability Scale(SDS), compared to placebo at Week 2 (p=0.003), and at every time pointthereafter (p=0.002, at Week 6).

On all secondary endpoints including the following, DM/BU demonstratedstatistically significant improvement at Week 6 compared to placebo,reflecting increasing treatment effects over time: clinical response onthe MADRS total score (defined as ≥50%) (p<0.001); PGI-I (p=0.007);CGI-S (p=0.002); CGI-I (p=0.016); QIDS-SR-16 (p=0.001); SheehanDisability Scale (SDS) (p=0.002); and Q-LES-Q-SF (p=0.011).

DM/BU was well tolerated in the phase 3 clinical trial. The mostcommonly reported adverse events in the DM/BU arm were dizziness,nausea, headache, diarrhea, somnolence, and dry mouth. There was oneserious adverse event in the DM/BU arm which was deemed by theinvestigator not to be study-drug related. The rates of discontinuationdue to adverse events were low in both treatment groups (6.2% for DM/BUand 0.6% for placebo). Treatment with DM/BU was not associated withpsychotomimetic effects or weight gain.

Example 7

A Phase 3, randomized, double-blind, active controlled trial wasconducted to assess the efficacy and safety of DM/BU in the treatment oftreatment resistant depression (TRD). Patients with major depressivedisorder (MDD) who had previously failed one or two antidepressanttreatments were treated in an open-label fashion with 150 mg bupropiontwice daily (300 mg total daily dose) (n=799, n represents of number ofpatients) during a 6-week lead-in period. Patients who failed to respondto bupropion during this lead-in period were randomized in a 1:1 ratioto treatment with bupropion at this same total daily dose (n=156), or totreatment with DM/BU (45 mg dextromethorphan/105 mg bupropion) twicedaily (90 mg dextromethorphan/210 mg bupropion total daily dose)(n=156), for 6 weeks. Inclusion criteria for the open-label periodincluded males or females 18-65 years of age, a history of inadequateresponse to 1 or 2 prior antidepressant treatments, established by theAntidepressant Treatment Response Questionnaire (ATRQ), and a HamiltonDepression Rating Scale (HAMD-17) total score of ≥18. Inclusion criteriafor the double-blind period included inadequate response to 2 or 3 priorantidepressant treatments, including open-label period failure.Exclusion criteria included a history of electroconvulsive therapy,vagus nerve stimulation, transcranial magnetic stimulation or anyexperimental central nervous system treatment during the current episodeor in the past 6 months, schizophrenia, bipolar disorder, obsessivecompulsive disorder, psychiatric symptoms secondary to any other generalmedical condition.

Demographics and baseline characteristics are shown in Table 7 below.Study completion rates were similar across both treatment groups, 89%for dextromethorphan/bupropion and 94% for bupropion.

TABLE 7 Demographics and Baseline Characteristics Dextromethorphan (45Bupropion mg)/Bupropion (105 mg) (150 mg) Age (years) 44.3 (12.19) 45.1(12.56) Female Gender, n (%) 101 (65.6%) 97 (62.6%) Race, n (%) White100 (64.9%) 106 (68.4%) Black or African American 41 (26.6%) 39 (25.2%)Asian 2 (1.3%) 6 (3.9%) Other or Not Reported 11 (7.1%) 4 (2.6%) BMI(mg/kg²) 29.9 (5.85) 29.5 (5.64) MADRS Total Score 33.4 (5.61) 33.2(5.17) CGI-S Score 4.6 (0.61) 4.6 (0.54) Data are mean (SD) unlessotherwise stated Abbreviations: BMI = Body Mass Index; CGI-S = ClinicalGlobal Impression-Severity; MADRS = Montgomery-Asberg Depression RatingScale

The change in depressive symptoms over time was measured using theMontgomery-Åsberg Depression Rating Scale (MADRS) and the QuickInventory of Depressive Symptomatology-Self-Rated (QIDS-SR-16). Theprimary endpoint was the change from baseline in the MADRS after 6 weeksof treatment. The key secondary endpoints were the change from baselinein the MADRS after 1 week of treatment, after 2 weeks of treatment, theaverage change over entire 6-week double-blind treatment period, and theSheehan Disability Scale (SDS). Other pre-specified secondary efficacyvariables included the Cognitive subscale of the Massachusetts GeneralHospital Cognitive and Physical Functioning Questionnaire (CPFQ), andthe Hamilton Anxiety Scale (HAM-A).

As shown in FIG. 18, DM/BU rapidly and significantly improved symptomsin patients with TRD as measured by MADRS averaged over the entire6-week treatment period, a key secondary endpoint, with mean reductionsof 8.6 for DM/BU (n=154) versus 6.7 for bupropion (n=155) (p=0.031). Therapid onset of action with DM/BU treatment was demonstrated withstatistically significant mean MADRS reductions at Week 1, the earliesttime point measured, of 5.2 versus 3.6 respectively for DM/BU andbupropion (p=0.02), and at Week 2 of 8.0 versus 6.1 respectively forDM/BU and bupropion (p=0.035), both time points being key secondaryendpoints. At Week 6 (primary endpoint), DM/BU demonstrated anumerically greater improvement in MADRS, with mean reductions of 11.6for DM/BU versus 9.4 for bupropion (p=0.117), but did not reachstatistical significance on the Week 6.

As shown in FIG. 19, DM/BU rapidly and significantly improved depressivesymptoms in patients with TRD as measured by the Quick Inventory ofDepressive Symptomatology-Self-Rated (QIDS-SR-16) averaged over theentire 6-week treatment period, with mean reductions of 3.3 for DM/BUversus 2.3 for bupropion (p=0.013).

As shown in FIG. 20, rates of remission from depression (defined asQIDS-SR-16 55) were statistically significantly greater for DM/BUcompared to bupropion at Week 1 (p=0.001) and at every time pointevaluated thereafter, being achieved by 18.2% of DM/BU patients comparedto 8.2% of bupropion patients at Week 6 (p=0.012).

As shown in FIG. 21, DM/BU significantly improved cognitive function inpatients with TRD as compared to bupropion, assessed using the Cognitivesubscale of the Massachusetts General Hospital Cognitive and PhysicalFunctioning Questionnaire (CPFQ) (p=0.011). Cognitive dysfunction iswell documented in the different phases of major depression, and playsan important role in functional recovery from major depression. Theimprovement in cognitive function with DM/BU was rapid as compared tobupropion, reaching statistical significance as early as Week 2 (p=0.01)and at every time point evaluated thereafter. The Cognitive subscale ofthe CPFQ assesses sharpness/mental acuity, and the ability tofocus/maintain attention, to remember/recall information, and to findwords. Statistical significance for the superiority of DM/BU versusbupropion was also achieved for the entire CPFQ (p=0.014), whichassesses physical in addition to cognitive functioning.

DM/BU rapidly and significantly reduced anxiety symptoms in patientswith TRD as compared to bupropion, assessed using the Hamilton AnxietyScale (HAM-A) (p=0.009). DM/BU demonstrated numerical improvement versusthe active comparator bupropion for all other efficacy variablesassessed.

DM/BU was well tolerated in the trial. The most commonly reportedadverse events in the DM/BU arm were dizziness and nausea. The rates ofdiscontinuation due to adverse events were low in both treatment groups(2.6% for DM/BU and 1.9% for bupropion). There were three seriousadverse events in the DM/BU arm, consisting of migraine; overdose; andsuicidal ideation, which occurred more than one week after the cessationof treatment. Treatment with DM/BU was not associated withpsychotomimetic effects, weight gain, or sexual dysfunction. Adverseevents are listed in Table 8 below.

TABLE 8 Treatment-Emergent Adverse Events Double-blind Period^(b)Open-label Period DM/BU (N = 154) BU (N = 156) BU (n = 310) Any TEAE^(a) 67 (43.5%) 61 (39.1%) 135 (43.5)  Dizziness 13 (8.4%) 0  9 (2.9%)Nausea  8 (5.2%) 3 (1.9%) 22 (7.1%) Dry mouth  6 (3.9%) 3 (1.9%) 13(4.2%) Headache  4 (2.6%) 7 (4.5%) 14 (4.5%) Insomnia  3 (1.9%) 5 (3.2%)19 (6.1%) Constipation  3 (1.9%) 3 (1.9%) 13 (4.2%) Anxiety  2 (1.3%) 011 (3.5%) Irritability 0 2 (1.3%) 10 (3.2%) Abbreviations: AE = adverseevent. Data presented as number of subjects (% of subjects)^(a)Treatment-emergent AEs occurring in ≥3 subjects during theopen-label period or ≥5% of subjects during the double-blind period arereported. ^(b)In double-blind period, treatment-emergent AE is definedas any AE with an onset on or after date of randomization and prior toor on visit 9 date or period 2 early termination date.

Example 8

A Phase 2/3 randomized, double-blind, controlled, multicenter, U.S.clinical trial was conducted to evaluate the efficacy and safety ofDM/BU in patients with agitation associated with Alzheimer's disease. Atotal of 366 patients with a diagnosis of probable Alzheimer's diseaseand clinically meaningful agitation associated with their disease wererandomized, initially in a 1:1:1 ratio, to receive DM/BU(dextromethorphan/bupropion, dose escalated from 30 mg/105 mg once dailyin the first week, to 30 mg/105 mg twice daily in the second week, to 45mg/105 mg twice daily thereafter), bupropion (dose escalated from 105 mgonce daily in the first week to 105 mg twice daily thereafter), ormatching placebo, for 5 weeks. An independent data monitoring committeeperformed an interim futility analysis and recommended no furtherrandomization to the bupropion arm. Subsequently, patients wererandomized in a 1:1 ratio to receive DM/BU or placebo. Total patientsrandomized were 159, 49, and 158 to the DM/BU, bupropion, and placeboarms, respectively. The mean Cohen-Mansfield Agitation Inventory (CMAI)total scores at baseline were 60.8, 66.1, and 59.3, respectively for theDM/BU, bupropion, and placebo groups. The minimum score on the CMAI is29, corresponding to the total absence of symptoms, with higher scorescorresponding to greater agitation. The primary endpoint of the studywas the change from baseline in the CMAI total score at Week 5. P-valueswere calculated based on least square mean estimates.

Inclusion criteria included male or female 65-90 years of age, diagnosisof probable Alzheimer's disease, according to the 2011 NIA-AA criteria,diagnosis of agitation, according to the IPA provisional definition ofagitation, MMSE score between 10 and 24, an NPI-AA score ≥4, andcommunity dwelling. Exclusion criterial included dementia ofnon-Alzheimer's type and current use of a selective serotonin reuptakeinhibitor and/or a serotonin and norepinephrine inhibitor (SSRI/SNRI).Demographics and baseline characteristics are shown in Table 9 below.

TABLE 9 Demographics and Baseline Characteristics DM/BU BupropionPlacebo (n = 152) (n = 49) (n = 156) Age (years) 75.2 (5.71) 76.4 (6.13)75.1 (5.96) Female Gender, n (%) 86 (56.6%) 22 (44.9%) 91 (58.3%) Race,n (%) White 136 (89.5%) 43 (87.8%) 128 (82.1%) Black or African 11(7.2%) 5 (10.2%) 25 (16.0%) American Asian 1 (0.7%) 0 1 (0.6%) Other orNot Reported 4 (2.6%) 1 (2.0%) 2 (1.3%) CMAI Score 60.7 (17.40) 66.1(19.65) 59.4 (15.60) CGI-S (agitation) 4.2 (0.77) 4.4 (0.82) 4.2 (0.65)NPI-A/A Score 7.2 (2.17) 6.9 (2.45) 6.8 (2.07) MMSE 18.7 (3.76) 17.8(4.19) 18.8 (3.70) mITT population. Data are mean (SD) unless otherwisestated. Abbreviations: BMI = Body Mass Index; BU = bupropion; CGI-S =Clinical Global Impression-Severity; CMAI = Cohen-Mansfield AgitationInventory; DM = dextromethorphan; mITT = modified intent to treat; MMSE= Mini-mental state examination; NPI-A/A = NeuropsychiatricInventory-Agitation and Aggressive domain.

As shown in FIG. 22, DM/BU met the primary endpoint by demonstrating astatistically significant mean reduction in the Cohen MansfieldAgitation Inventory (CMAI) total score compared to placebo at Week 5,with mean reductions from baseline of 15.4 points for DM/BU (n=152),10.0 for BU 9n=49), and 11.5 points for placebo (n=156) (p=0.010).

As shown in FIG. 23, These results represent a mean percentage reductionof CMAI from baseline of 48% for DM/BU versus 38% for placebo. The CMAIis a 29-item caregiver-rated scale that assesses the frequency ofagitation-related behaviors in patients with dementia, includingexcessive motor activity such as pacing and restlessness, verbalaggression such as screaming and shouting, and physical aggression suchas grabbing, pushing, and hitting. DM/BU was also statistically superiorto bupropion on the CMAI total score (p<0.001) at week 5, demonstratingcomponent contribution.

DM/BU rapidly improved agitation symptoms. DM/BU numerically separatedfrom placebo at Week 2 with a mean reduction from baseline in the CMAItotal score of 11.5 points for DM/BU compared to 8.7 points for placebo(p=0.069).

DM/BU demonstrated a statistically significant mean reduction frombaseline in the CMAI total score of 13.8 points for DM/BU compared to9.7 points for placebo at Week 3 (p=0.007), with statisticalsignificance for this measure maintained thereafter.

As shown in FIG. 24, a statistically significantly greater proportion ofpatients achieved a clinical response on the CMAI, defined as a 30% orgreater improvement from baseline, with DM/BU as compared to placebo(73% versus 57%, p=0.005). These results were consistent withclinicians' global assessments of change measured using the modifiedAlzheimer's Disease Cooperative Study-Clinical Global Impression ofChange for Agitation (mADCS-CGIC). DM/BU demonstrated statisticallysignificantly greater improvement in agitation as compared to placebo onthis measure (p=0.036).

DM/BU was safe and well tolerated in the trial. The most commonlyreported adverse events in the DM/BU arm were somnolence (8.2% for DM/BUversus 4.1% for bupropion and 3.2% for placebo), dizziness (6.3%, 10.2%,3.2%, for DM/BU, bupropion, and placebo arms respectively), and diarrhea(4.4%, 6.1%, 4.4%, for DM/BU, bupropion, and placebo arms respectively).The rates of discontinuation due to adverse events were 1.3%, 2.0%, and1.3% in the DM/BU, bupropion, and placebo arms, respectively. Seriousadverse events were reported in 3.1% of patients treated with DM/BU,compared to 8.2% of bupropion, and 5.7% of placebo-treated patients. Noserious adverse events were deemed to be related to study drug in anytreatment arm. There was one death in the placebo arm, one in thebupropion arm, and none in the DM/BU arm. There was no evidence ofcognitive decline for patients treated with DM/BU as shown by theMini-Mental State Examination (MMSE), a widely utilized measure ofgeneral cognitive function. Treatment with DM/BU was not associated withsedation. Adverse events are listed in Table 10 below.

TABLE 10 Treatment-Emergent Adverse Event DM/BU Bupropion Placebo (n =159) (n = 49) (n = 158) Subjects with any 70 (44.0%) 30 (61.2%) 52(32.9%) TEAE Somnolence 13 (8.2%) 2 (4.1%) 5 (3.2%) Dizziness 10 (6.3%) 5 (10.2%) 5 (3.2%) Diarrhea  7 (4.4%) 3 (6.1%) 7 (4.4%) Headache  6(3.8%) 3 (6.1%) 5 (2.5%) Falls  4 (2.5%)  7 (14.3%) 3 (1.9%) Fatigue  3(1.9%)  5 (10.2%) 2 (1.3%) Insomnia  1 (0.6%) 3 (6.1%) 3 (1.9%) SeriousAEs  5 (3.1%) 4 (8.2%) 9 (5.7%) Discontinuation due  2 (1.3%) 1 (2.0%) 2(1.3%) to AEs Deaths 0 1 (2.0% 1 (0.6%) Abbreviations: AE = adverseevent; TEAE = Treatment-emergent adverse event. Safety Population, datapresented as number of subjects (% of subjects). Treatment-emergent AEsoccurring in ≥5% of subjects in any treatment group are presented.

Example 9

An open label study was started with 47 patients having major depressivedisorder who had received two or more treatments in the current majordepressive episode prior to being treated with a combination of 45 mg ofdextromethorphan hydrobromide and 105 mg of bupropion hydrochloride,given twice a day. Preliminary results for the ongoing study aredepicted in Table 11 below.

TABLE 11 Week Week Week Week Week Week Baseline 1 2 4 6 8 12 MADRS 33.2823.11 18.28 14.58 9.20 9.11 11.15 MADRS −10.2 −15.2 −18.7 −24.1 −24.0−22.2 Change from BL

Example 10

The open label study of Example 9 was continued. A total of 70 patientswere enrolled who had ongoing symptoms of depression despite receivingtreatment with two or more prior antidepressants during the currentmajor depressive episode. Patients were treated with a 45 mgdextromethorphan-105 mg bupropion modulated delivery tablet twice dailyfor up to 12 months. The results are summarized in Table 12.

TABLE 12 MADRS Reduction: mean reduction of MADRS score from baseline.MADRS Timepoint Reduction Baseline 0 1 week −10.4 2 weeks −14.7 6 weeks−20.6 6 months −22.9 1 year −26.3

FIG. 25 depicts the reduction in MADRS Score from baseline from thistrial DM/BU as compared to the combination of dextromethorphan andquinidine (DM/Q) as reported in Murrough (Journal of Affective Disorders218 (2017) 277-283, FIG. 3A).

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as amounts, percentage, and so forth usedin the specification and claims are to be understood in all instances asindicating both the exact values as shown and as being modified by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the specification and attached claimsare approximations that may vary depending upon the desired propertiessought to be obtained. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques.

The terms “a,” “an,” “the” and similar referents used in the context ofdescribing the embodiments (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein is intended merely to better illuminate theembodiments and does not pose a limitation on the scope of any claim. Nolanguage in the specification should be construed as indicating anynon-claimed element essential to the practice of the claims.

Groupings of alternative elements or embodiments disclosed herein arenot to be construed as limitations. Each group member may be referred toand claimed individually or in any combination with other members of thegroup or other elements found herein. It is anticipated that one or moremembers of a group may be included in, or deleted from, a group forreasons of convenience and/or to expedite prosecution. When any suchinclusion or deletion occurs, the specification is deemed to contain thegroup as modified thus fulfilling the written description of all Markushgroups if used in the appended claims.

Certain embodiments are described herein, including the best mode knownto the inventors for carrying out the claimed embodiments. Of course,variations on these described embodiments will become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventor expects skilled artisans to employ such variations asappropriate, and the inventors intend for the claimed embodiments to bepracticed otherwise than specifically described herein. Accordingly, theclaims include all modifications and equivalents of the subject matterrecited in the claims as permitted by applicable law. Moreover, anycombination of the above-described elements in all possible variationsthereof is contemplated unless otherwise indicated herein or otherwiseclearly contradicted by context.

In closing, it is to be understood that the embodiments disclosed hereinare illustrative of the principles of the claims. Other modificationsthat may be employed are within the scope of the claims. Thus, by way ofexample, but not of limitation, alternative embodiments may be utilizedin accordance with the teachings herein. Accordingly, the claims are notlimited to embodiments precisely as shown and described.

What is claimed is:
 1. A method of increasing dextromethorphan plasmalevels in a human being, comprising orally administering, once a day ortwice a day, a dosage form comprising bupropion and dextromethorphan tothe human being, wherein the human being is an extensive metabolizer ofdextromethorphan in need of treatment with dextromethorphan, wherein thedosage form contains about 75 mg to about 150 mg of the bupropion andabout 45 mg of the dextromethorphan and bupropion and dextromethorphanare the only therapeutically active agents to be administered, whereinthe dosage form is orally administered for at least eight consecutivedays, and wherein on the eighth day that the dosage form is orallyadministered, the human being has a C_(min) of dextromethorphan that isat least about 40 ng/mL.
 2. The method of claim 1, wherein the dosageform contains about 45 mg of the dextromethorphan and about 100 mg toabout 140 mg of the bupropion.
 3. The method of claim 1, wherein on theeighth day that the dosage form is orally administered, the human beinghas a C_(min) of dextromethorphan that is at least about 15 times theC_(min) that would be achieved by orally administering the same amountof the dextromethorphan without bupropion for eight consecutive days. 4.The method of claim 1, wherein on the eighth day that the dosage form isorally administered, the human being has an AUC₀₋₁₂ of dextromethorphanthat is at least about 700 ng·hr/mL.
 5. The method of claim 1, whereinon the eighth day that the dosage form is orally administered, the humanbeing has an AUC₀₋₁₂ of dextromethorphan that is about 750 ng·hr/mL. 6.The method of claim 1, wherein on the eighth day that the dosage form isorally administered, the human being has a C_(max) of dextromethorphanthat is at least about 70 ng/mL.
 7. A method of increasingdextromethorphan plasma levels in a human being, comprising orallyadministering, once a day or twice a day, a dosage form comprisingbupropion and dextromethorphan to the human being, wherein the humanbeing is an extensive metabolizer of dextromethorphan in need oftreatment with dextromethorphan, wherein the dosage form contains about75 mg to about 150 mg of the bupropion and about 45 mg of thedextromethorphan and bupropion and dextromethorphan are the onlytherapeutically active agents to be administered, wherein the dosageform is orally administered for at least eight consecutive days, andwherein on the eighth day that the dosage form is orally administered,the human being has a C_(min) of dextromethorphan that is about 45ng/mL.
 8. The method of claim 7, wherein on the eighth day that thedosage form is orally administered, the human being has a C_(min) ofdextromethorphan that is at least about 15 times the C_(min) that wouldbe achieved by orally administering the same amount of thedextromethorphan without bupropion for eight consecutive days.
 9. Themethod of claim 7, wherein the bupropion and the dextromethorphan are inseparate domains, layers, or phases within the dosage form.
 10. Themethod of claim 9, wherein the domains, the layers, or the phasescontaining the bupropion provide sustained release of bupropion and thedomains, the layers, or the phases containing the dextromethorphanprovide immediate release of dextromethorphan.
 11. The method of claim7, wherein the human being is at risk of experiencing an adverse eventas a result of being treated with dextromethorphan.
 12. The method ofclaim 7, wherein the human being is at risk of experiencing an adverseevent as a result of being treated with bupropion.
 13. The method ofclaim 7, wherein the dosage form is orally administered for at least 30consecutive days.
 14. The method of claim 7, wherein on the eighth daythat the dosage form is orally administered, the human being isconverted to a poor metabolizer of dextromethorphan.
 15. The method ofclaim 7, wherein the human being is at least 18 years of age.
 16. Amethod of increasing dextromethorphan plasma levels in a human being,comprising orally administering, once a day or twice a day, a dosageform comprising bupropion and dextromethorphan to the human being,wherein the human being is an extensive metabolizer of dextromethorphanin need of treatment with dextromethorphan, wherein the dosage formcontains about 75 mg to about 150 mg of the bupropion and about 45 mg ofthe dextromethorphan and bupropion and dextromethorphan are the onlytherapeutically active agents to be administered, wherein the dosageform is orally administered for at least eight consecutive days, andwherein on the eighth day that the dosage form is orally administered,the human being has a C_(min) of dextromethorphan that is about 40 ng/mLto 119.3 ng/mL.
 17. The method of claim 16, wherein the dosage formcontains about 45 mg of the dextromethorphan and about 100 mg to about140 mg of the bupropion.
 18. The method of claim 16, wherein on theeighth day that the dosage form is orally administered, the human beinghas a C_(min) of dextromethorphan that is at least about 15 times theC_(min) that would be achieved by orally administering the same amountof the dextromethorphan without bupropion for eight consecutive days.19. The method of claim 16, wherein the dosage form provides sustainedrelease of bupropion and immediate release of dextromethorphan.
 20. Themethod of claim 16, wherein the dextromethorphan or the bupropion isdeuterium-modified.
 21. The method of claim 1, wherein the human beingis at risk of experiencing an adverse event as a result of being treatedwith bupropion.
 22. The method of claim 16, wherein the human being isat risk of experiencing an adverse event as a result of being treatedwith bupropion.